ROPERTY  OP 


MEMCAL 


HE  PROPERTY  OP 

al  College  of  tie  Pacific. 


DONATED  BY 


STUDENTS  HISTOLOGY 


A    COURSE    OF   NORMAL    HISTOLOGY 

FOE    STUDENTS  AND 
PEACTITIONEES    OF    MEDICINE 


BY 

MAURICE    N.    MILLER,    M.D. 
.^' 

Late    Director    of  the    Department    of  Normal   Histology   in   Loomis1    Laboratory, 
University    of  the    City    of  New    York 

REVISED     BY 

HERBERT    U.   WILLIAMS,    M.D. 

Professor    of  Pathology    and   Bacteriology,  Medical    Department, 
University    of  Buffalo 


THIRD     REVISED     EDITION 
PROFUSELY  ILLUSTRATED 


NEYvT    YORK 

WILLIAM    WOOD    &    COMPANY 

1898 


COPYRIGHT  BY 
WILLIAM    WOOD    &    COMPANY 

1898 


J.  Horace  McFarland  Company 
Harrisburg,  Pa. 


1*59  f 


PREFACE 

This  volume  has  been  prepared  with  a  view  of  aiding  the 
instructors  and  students  of  the  laboratory  classes  which  are 
under  my  direction. 

It  is  also  presented  with  the  hope  that  it  may  be  useful  to 
other  instructors. 

Again,  students  often  wish  to  continue  microscopical  work 
during  the  interim  of  college  attendance ;  to  such,  it  is  my 
belief,  these  pages  will  have  some  value. 

Still  again,  very  many  practitioners,  not  having  had,  during 
pupilage,  advantages  equal  to  those  provided  by  the  modern 
laboratory  equipment,  wish  to  acquire  more  knowledge  of 
microscopy,  for  its  value  in  practical  medicine.  To  such 
workers,  also,  I  desire  to  be  useful. 

So  much  technique  has  been  introduced  as  has  been  found 
to  be  of  absolute  necessity,  and  no  more.  The  processes  for 
the  preparation  and  exhibition  of  tissues  are  generally  simple 
and  always  practicable. 

In  the  description  of  organs,  I  assume  that  the  student  has 
a  fair  knowledge  of  gross  anatomy,  but  knows  nothing  of  his- 
tology. The  scheme  or  plan  of  the  structure  is  first  described 
— using  diagrams  where  requisite  to  clearness — after  which  the 
mode  of  preparing  the  sections  is  indicated,  and,  under  prac- 
tical demonstration,  every  histological  detail  tabulated  in  proper 
order.  The  ^drawings  will,  I  believe,  aid  in  the  recognition  of 
such  elements  in  the  field  of  the  microscope. 

The  illustrations  are  exact  reproductions,  by  photography, 
of  my  own  pen  -  pictures  ;  and  distinction  must  always  be  made 
between  the  drawings  which  are  schematic — used  to  emphasize 

("i) 


IV  PREFACE 

the  plan  of  structures  —  and  those  drawn  from  the  tissue  as 
seen  in  the  microscope. 

Our  literature  abounds  in  excellent  works  for  the  advanced 
student,  and  this  volume  is  designed  to  pave  the  way  for  their 
appreciation. 

I  desire  to  record  my  high  appreciation  of  the  aid  of  Drs. 
Charles  T.  Jewett,  Egbert  Le  Fevre,  E.  Eliot  Harris,  Milton 
Turnure,  H.  Pereira  Mendes,  J.  Gorman,  A.  M.  Lesser,  J.  Alex- 
ander Moore,  Robert  Eoberts,  Esq.,  Warden,  and  Mr.  John 
Burns,  Clerk  of  Charity  Hospital,  in  facilitating  my  access  to 
valuable  tissue  for  the  illustrations  and  for  my  own  studies. 

My  thanks  are  due  my  First  Assistant,  Dr.  F.  T.  Reyling, 
for  his  indefatigable  efforts  in  furthering  the  work ;  and  to 
Mr.  A.  J.  Drummond,  for  photographical  favors. 

MAURICE    N.   MILLER. 
NEW  YORK,  June  1st,  1887. 


PREFACE   TO   THIRD  REVISED  EDITION 

A  revision  of  Miller's  Microscopy  became  necessary,  partly  on 
account  of  the  advances  made  in  histology  during  the  last  ten 
years,  and  partly  because  of  the  increasing  tendency  in  medical 
schools  to  devote  more  time  to  laboratory  studies.  Substantially 
all  of  the  original  matter  has  been  retained,  although  somewhat 
rearranged ;  and  where  new  matter  has  been  inserted,  the 
attempt  has  been  made  to  'give  it  the  form  which  was  the 
peculiarity  of  the  original,  namely,  in  being  written  from  the 
point  of  view  of  the  student,  and  not  of  the  teacher.  In  pre- 
paring the  various  additions,  the  standard  text -books  on  his- 
tology have  been  constantly  consulted. 

BUFFALO,  N.  Y.,  August,  1898. 


CONTENTS 


PART  FIRST 

TECHNOLOGY 

THE    LABORATORY    MICROSCOPE 

PAGE 

Description  of  the  Stand 1 

Lenses 2 

General  Adjustment 4 

Adjustment  for  Illumination 4 

Adjustment  for  Focus 5 

Method  in  Observation •  6 

Conservation  of  the  Eyesight 7 

Magnifying  Power 7 

Measurement  of  Objects 8 

Sketching  from  the  Instrument 9 

PREPARATION    OF    TISSUES    FOR   MICROSCOPICAL 
PURPOSES 

Teasing  of  Tissues 9 

Section  Cutting 10 

Free-hand  Section  Cutting 10 

Section  Cutting  with  the  Stirling  Microtome 12 

Section  Cutting  with  the  Larger  Microtomes 15 

Sharpening  Knives — Honing  and  Stropping 16 

Supporting  Tissues  for  Cutting 18 

Paraffin  Soldering 18 

The  Freezing  Microtome 19 

Fixing  or  Hardening  Fluids 20 

Alcohol  Hardening 21 

Mailer's  Fluid • 22 

Orth's  Fluid 22 

Formaldehyde 22 

Picric  Alcohol 23 

Osmic  Acid 23 

Flemming's  Solution 23 

Chromic  Acid 24 

Erlicki's  Fluid 24 

(v) 


VI  CONTENTS 

PAGE 

Decalcifying  Fluid 24 

Dissociating  Fluid 25 

Imbedding— Paraffin 25 

"        — Celloidin 26 

Staining  Methods  in  General 27 

Hsematoxylin 28 

Eosin 28 

Carmine    . 29 

Weigert-Pal  Method 30 

Aniline  Dyes 31 

Van  Gieson's  Stain 32 

Ehrlich  Tricolor  Stain  .    .                32 

Metallic  Impregnations — Nitrate  of  Silver 33 

Golgi's  Method .  33 

Injection  Methods 34 

Clearing  Agents 35 

Mounting  Media 35 

Hsematoxylin  Staining  Process 36 

Heematoxylin  and  Eosin  Double  Staining         38 

Borax -Carmine  Staining  Process 39 

Cleaning  Slides  and  Cover-glasses 41 

Mounting  Methods 41 

Labeling  Slides    .    .           42 

Care  of  the  Microscope 43 


PAKT   SECOND 
STRUCTURAL   ELEMENTS 

PRELIMINARY    STUDY 

Form  of  Objects 45 

Movement  of  Objects 46 

Extraneous  Substances   . 47 

STRUCTURAL   ELEMENTS 

Cells 49 

Cell  Distribution 50 

Cell  Division— Karyokinesis 51 

Classification  of  Tissues 53 

Embryonic  Derivation  of  Tissues 54 

Epithelium 54 

Distribution  of  Epithelium 55 

Squamous,  Stratified,  and  Transitional  Epithelium 55 

Pavement  Epithelium .  56 

Columnar  Epithelium    .    .           57 

Ciliated  Columnar  Epithelium 58 


CONTENTS  Vii 

PAGE 

Glandular  Epithelium 59 

Endothelium— Serous  Membranes 60 

CONNECTIVE    (FIBEOUS)    TISSUES 

White    Fibrous  Tissue —62- 

Yellow  Elastic  Tissue 63 

Adipose  Tissue 65 

CARTILAGE 

Hyaline  Cartilage 67 

White  Fibro- Cartilage           ...           .    .           .        68 

Elastic  Cartilage 68 

BONE 

Bone 70 

Periosteum .- 73 

Marrow 73 

Development  of  Bone 73 


SPECIAL  CONNECTIVE    TISSUES  (page  76) 

MUSCULAR    TISSUE 

Non-striated  Muscle 76 

Striated  Muscle 78 

Cardiac  Muscle 80 

BLOOD 

Red  Corpuscles 81 

Blood-plates 82 

White  Corpuscles -83 

Enumeration  of  Blood-corpuscles 87 

Haemoglobin 89 

Fibrin 90 

Effect  of  Reagents 90 

Development  of  Red  Blood -corpuscles 91 


PART    THIRD 
ORGANS 

THE    SKIN 

Layers  or  Strata 92 

Hairs 95 

Sudoriferous  Glands 97 


viii  CONTENTS 

PAGE 

Sebaceous  Glands 98 

Nails 98 

Practical  Demonstration 98 


THE    CIRCULATORY  SYSTEM 

The  Heart 102 

Blood-vessels : 102 

Development  of  Capillaries 105 

THE   LYMPHATIC    SYSTEM 

General  Description 10G 

Lymph-channels 107 

Practical   Demonstration,    Lymph-channels    of    Central    Tendon    of    the 

Diaphragm f 108 

Lymphatic  Nodes  or  Glands  .    P Ill 

Practical  Demonstration,  Mesenteric  Lymph-node 113 

THE    SPLEEN 

Scheme  of  Organ 117 

Practical  Demonstration 118 

THE    THYMUS    BODY 

General  Description 121 

Practical  Demonstration  .  121 


THE    RESPIRATORY   ORGANS 

The  Larynx  and  Trachea ]  23 

The  Lungs .••••' 123 

Bronchial  Tubes 123 

Practical  Demonstration 125 

Pulmonary  Blood-vessels 128 

Pleura .- 128 

Pulmonary  Alveoli 128 

Practical  Demonstration,  Lung  of  Pig 131 

Practical   Demonstration,   Human  Lung 133 

Foetal  Lung     . 134 

THE    TEETH 

The  Pulp 135 

Dentine 135 

Enamel 137 

Cementum 137 

Practical  Demonstration  .  137 


CONTENTS  ix 
GLANDS 

PAGE 

Typical  Glandular  Histology     140 

Tubular  Glands 140 

Coiled  Tubular  Glands 140 

Branched  Tubular  Glands ~143~ 

Acinous  Glands * 143 

Parotid  Gland 143 

Submaxillary  Gland 144 

Pancreas 145 

Practical  Demonstration,  Parotid  Gland,  Submaxillary  Gland,  Pancreas    .  146 

Thyroid  Gland 148 

THE    ALIMENTARY   CANAL 

The  Mouth  and  Pharynx .  149 

The  (Esophagus 150 

Practical  Demonstrations" 150 

General  Histology  of  the  Stomach  and  Intestines 151 

The  Stomach 152 

Practical  Demonstration  . 155 

Small  Intestine 156 

Practical  Demonstration 160 

Duodenum,  Vermiform  Appendix,  Large  Intestine 162 

THE    LIVER 

General  Scheme      163 

The  Portal  Canals 165 

The  Lobular  Parenchyma 165 

Practical  Demonstration,  Liver  of  Pig 167 

Practical  Demonstration,  Human  Liver      170 

Practical  Demonstration,  The  Portal  Canals 172 

Practical  Demonstration,  The  Lobular  Parenchyma 173 

Practical  Demonstration,  Origin  of  Bile -ducts 176 

Gall-bladder 177 

THE    KIDNEY 

General  Description 178 

The  Tubuli  Uriniferi 180 

Blood-vessels '.  183 

Practical  Demonstration,  with  Low-power 186 

Practical  Demonstration,  The  Cortical  Portion 187 

Practical  Demonstration,  The  Medullary  Portion 192 

Pelvis  of  the  Kidney  and  Ureter 193 

Urinary  Bladder 19 1 

Urethra".  .  196 


X  CONTENTS 

FEMALE  GENERATIVE  ORGANS 

PAGE 

Vagina  and  Uterus— Practical  Demonstration ]  97 

Fallopian  Tube — Practical  Demonstration     ...     •  .    .    . 202 

Ovary 203 

Adult  Human  Ovary— Practical  Demonstration 203 

Formation  of  the  Ovum 206 

Ovary  of  Human  Infant— Practical  Demonstration 206 

Mammary  Gland 208 

MALE    GENERATIVE   ORGANS 

Testicle — General  Description 209 

Practical  Demonstration 211 

Spermatozoa 211 

Prostate  Gland 212 

Erectile  Tissue 212 

SUPRARENAL   BODY 

Practical  Demonstration 213 

THE   NERVOUS   SYSTEM 

Structural  Elements 216 

Nerve-fibers 216 

Nerve-trunks 217 

Practical  Demonstration 219 

Nerve-cells 219 

Neuroglia 222 

Peripheral  Nerve-endings       223 

THE    SPINAL   CORD 

General  Description 226 

Division  into  Tracts 228 

Practical  Demonstration  .      .           229 

Relation  of  Ganglion- cells  and  Nerve -fibers 233 

THE    BRAIN 

Membranes 235 

Cerebrum — Practical  Demonstration 237 

Layers  of  the  Cerebral  Cortex 238 

Paths  followed  by  Nerve -fibers  in  the  White  Matter 239 

Cerebellum— Practical  Demonstration 240 

INDEX    (page   245) 


LIST  OF  ILLUSTRATIONS 


FIG.  PAGE 

1.  Microscope 2 

2.  Relation  of  Objective  to  Eye-piece 3 

3.  English  and  Metric  Scales 8 

4.  Free-hand  Section  Cutting 11 

5.  Stirling's  Microtome 12 

6.  Method  of  Imbedding  with  Pith,  Turnip,  etc 13 

7.  Section  Cutting  with  Stirling  Microtome .  14 

8.  Thoma  Microtome 14 

9.  Schanze  Microtome 15 

10.  Method  of  Honing  Razor 16 

11.  Turning  the  Razor  on  the  Hone 16 

12.  Paraffin  Soldering  Wire 18 

13.  Cementing  Hardened  Tissue  to  Cork 18 

14.  Freezing  Microtome 19 

15.  Using  Turn-table 36 

16.  Needle  for  Lifting  Sections 36 

17.  Diagram  Illustrating  Steps  in  Staining  with  Hgematoxylin 37 

18.  Diagram  Illustrating  Steps  in  Staining  with  Haeinatoxylin  and  Eosin.     39 

19.  Diagram  Illustrating  Steps  in  Staining  with  Borax-Carmine    ....  40 

20.  Section -lifters 41 

21.  Appearance  of    Balsam-mounted  Specimen 42 

22.  Mode  of   Handling  Cover-glass 42 

23.  Diagram  Showing  Effect  of   Oil  and  Air  Globules 46 

24.  Extraneous  Substances— Fibers,  etc 47 

25.  Extraneous  Substances — Starch,  etc 48 

26.  Elements  of    a  Typical  Cell 49 

27.  Structure  of    a  Cell-nucleus 50 

28.  Indirect  Cell  Division 51 

29.  Karyokinesis 52 

30.  Squamous  Epithelial  Cells  from  Mouth 56 

31.  Pavement   Epithelium 57 

32.  Columnar  Cells  from  Intestine 58 

33.  Ciliated  Columnar  Cells  from  Bronchus 58 

34.  Diagram  Showing  Organs  of   the  Oyster 59 

35.  Glandular  Cells  from  Liver 60 

36.  Frog's  Mesentery — Silver- staining 61 

37.  White  Fibrous  Tissue 63 

38.  Yellow  Elastic  Tissue 64 

39.  Transverse  Section  of   Ligamentum  Nuchse 64 

(xi) 


xii  LIST   OF  ILLUSTRATIONS 

FIO.  PAGE 

40.  Cells  containing  Fat 6G 

41.  Adipose  Tissue  from  Omentum 66 

42.  Hyaline  Cartilage  from  Bronchus 67 

43.  Fibro- Cartilage  from  Intervertebral  Disc 68 

44.  Elastic  Cartilage  from  Ear  of  Bullock 69 

45.  Bone — Showing  Laminated  Structure 69 

46.  Bone — Showing  Haversian  Systems 70 

47.  Bone — Showing  Sharpey's  Fibers 71 

48.  Contents  of    Haversian  Canals 71 

49.  Contents  of    Bone  Lacuna 72 

50.  Cells  from  Bed  Marrow 74 

51.  Developing  Bone 75 

52.  Non-striated  Muscular  Fiber 77 

53.  Striated  Muscular  Fiber '.'..' 78 

54.  Striated  Muscular  Fiber  from  Tongue 79 

55.  Cardiac  Muscular  Fiber .' 80 

56.  Corpuscular  Elements  of  Human  Blood 81 

57.  Diagram  of    Red  Blood-corpuscle 82 

58.  Blood  Showing  Blood-plates 83 

59.  Cover- glass,  Preparations  of  Blood 84 

60.  Varieties  of   Leucocytes .    .        .  85 

61.  Pipettes  for  Hsemocytometer 86 

62.  Disk  of   Haamocytometer 87 

63.  Magnified  Field  of    Haemocytometer 88 

64.  Crystals  of   Haemoglobin 89 

65.  Blood-corpuscles  of   the  Frog 90 

66.  Layers  of   the  Epidermis                       93 

67.  Structure  of   the  Derma — Injected 94 

68.  Hair  in  Transverse  Section 95 

69.  Hair  Follicle  .....                       96 

70.  Sudoriferous  Gland 97 

71.  Sebaceous  Gland   ...        98 

72.  Skin  in  Vertical  Section.              .    .        100 

73.  Diagrammatic  Section  of   Artery    ...            103 

74.  Blood-capillaries 104 

75.  Perivascular  Lymph-spaces   ...                    ...                107 

76.  Lymphatics  of   Central  Tendon  of   the  Diaphragm — Low-power     .    .  110 

77.  Lymphatics  of   Central  Tendon  of   the  Diaphragm — High-power    .    .  Ill 

78.  Lymph-node — Diagrammatic .112 

79.  Mesenteric  Lymph-node — Low-power        114 

80.  Mesenteric  Lymph-node — High-power 115 

81.  Blood-vessel  Arrangement  in  the  Spleen 117 

82.  Spleen 119 

83.  Thymus  Body     .                122 

84.  Bronchial  Tube— Small        124 

85.  Bronchial  Tube— Medium           127 

86.  Pulmonary  Lobule— Perspective       129 

87.  Pulmonary  Lobule — Longitudinal  Section 129 

88.  Pulmonary  Alveolus — Capillaries  Injected 130 


LIST   OF  ILLUSTRATIONS  Xlll 

FIG.  PAGE 

89.  Lung  of  Pig          132 

90.  Pulmonary  Alveolus  Showing  Lining 133 

91.  Diagrammatic  Section  of  Tooth 136 

92.  Section  of  Part  of  Tooth— High -power 139 

93.  Simple  Tubular  Gland _141_ 

94.  Coiled  Tubular  Gland ....  141 

95.  Branched  Tubular  Gland 142 

96.  Acinous  Gland 142 

97.  Parotid  Gland 144 

98.  Submaxillary  Gland 145 

99.  Pancreas 146 

100.  Stomach — Diagrammatic  Section 152 

101.  Cardiac  Gastric  Gland 153 

102.  Pyloric  Gastric  Gland ....  154 

103.  Stomach  of  Dog • 155 

104.  Diagram  Illustrating  Intestinal  Secretion 158 

105.  Diagram  of  Intestinal  Absorption     .    .            159 

106.  Small  Intestine  with  Peyer's  Patch 161 

107.  Liver — Diagram  Illustrating  Plan  of  Structure 164 

108.  Glandular  Cells  in  Connection  with  Blood-vessels  and  Ducts    .    .    .  166 

109.  Liver  of  Pig 168 

110.  Human  Liver — Low-power 171 

111.  Portal  Canal 173 

112.  Hepatic  Cells— Detached 174 

113.  Hepatic  Lobule  in  Transverse  Section 175 

114.  Bile-capillaries — Origin  of  Bile-duct 176 

115.  Kidney — Diagram  Illustrating  Plan  of  Structure 179 

116.  Kidney  Tubules— Isolated. '       ....  .181 

117.  Blood-vessels — Arrangement  in  Kidney .  183 

118.  Kidney — Low-power           186 

119.  Kidney— Cortex  in  Vertical  Section  .......        .  188 

120.  Kidney — Medulla  in  Longitudinal  Section 191 

121.  Kidney— Medulla  in  Transverse  Section .    .  192 

122.  Epithelium  of  Ureter 194 

123.  Epithelium  of  Urinary  Bladder          ....  195 

124.  Uterus  with  Vaginal  Cul-de-sac 198 

125.  External  Os  Uteri  .            .......  200 

126.  Vaginal  Epithelium 201 

127.  Fallopian  Tube 202 

128.  Ovary— Adult 204 

129.  Ovary— Child's 207 

130.  Mammary  Gland— Dog ...  208 

131.  Mammary  Gland — Dog ....  208 

132.  Testicle,   Diagram 209 

133.  Seminiferous  Tubules .  210 

134.  Spermatozoa r   211 

135.  Suprarenal  Body — Low-power     .                                                214 

136.  Suprarenal  Body— High-power 215 

137.  Nerve -fibers  .216 


XIV  LIST   OF  ILLUSTRATIONS 

FIG.  PAGK 

138.  Nerve -trunk — Transverse  Section      218 

139.  Two  Types  of  Ganglion -cells  .......        220 

140.  Diagram  of  a  Neurone ...  221 

141.  Neuroglia 222 

142.  Nerve-endings  in  the  Cornea 223 

143.  Tactile  Corpuscle 224 

144.  Pacinian  Corpuscle 224 

145.  Nerve-ending  in  Striated  Muscle 225 

146.  Diagram,  Spinal  Cord 226 

147.  Dorsal  Spinal  Cord 227 

148.  Lumbar  Spinal  Cord 228 

149.  Cervical  Spinal  Cord  .       230 

150.  Anterior  Horn — Gray  Matter— Cervical  Spinal  Cord 231 

151.  Ganglion  cells,  Anterior  Horn 233 

152.  Diagram,  Relations  of  Cells -and  Nerve-fibers  in  the  Spinal  Cord.   .  234 

153.  Layers  of   the  Cerebral  Cortex 236 

154.  Section  of  Cerebrum 237 

155.  Ganglion-cell  and  Neuroglia-cell — Cerebral  Cortex 239 

156.  Cerebellum — Low-power 240 

157.  Cerebellum — High-power 241 

158.  Cell  of   Purkinje 242 


STUDENTS  HISTOLOGY 


PART    FIRST 
TECHNOLOGY 


THE    LABORATORY    MICROSCOPE 

The  histologist  should  be  provided  with  a  microscope,  in  which 
the  principal  features  of  the  laboratory  instrument,  Fig.  1,  are 
embraced. 

The  body  A,  which  carries  the  optical  parts,  is  made  of  two 
pieces  of  brass  tubing,  one  sliding  within  the  other  and  providing 
for  alterations  in  length.  The  objectives,  B,  C,  D,  are  attached  to 
the  body  by  means  of  the  triple  nose-piece,  E.  The  nose-piece 
is  so  pivoted  that  either  objective  may  be  turned  into  the  optical 
axis  at  will.  The  eye-piece,  F,  slips  into  the  upper  part  of  the 
body  with  but  little  friction,  so  that  it  may  be  quickly  and 
easily  removed. 

The  coarse  or  quick  adjustment  for  focusing  consists  of  a  rack, 
G,  which  is  attached  to  the  body,  and  into  this  gears  a  small 
(concealed)  pinion  turned  by  the  milled  heads,  H. 

The  more  delicate  adjustments  are  accomplished  by  means  of  a 
micrometer  screw  acting  by  a  simple  mechanical  device  upon  an 
enclosed  spring  in  connection  with  a  prism  slide.  By  turning  the 
milled  head,  L,  the  body  of  the  instrument  is  raised  or  lowered,  as 
desired,  and  with  extreme  delicacy. 

The  stage,  M,  upon  which  objects  are  placed  for  examination, 
is  perforated,  and  an  iris  diaphragm  and  Abbe  condenser,  K,  may 
be  inserted.  The  iris  diaphragm  enables  one  to  alter  the  size  of 
the  opening  at  will.  Below  the  stage  an  arm  may  be  seen  which 
carries  a  sliding  fork  supporting  the  mirror,  N,  one  side  of  which 
is  plane  and  the  other  concave. 


STUDENTS  HISTOLOGY 


FIG.  1.    THE  MICROSCOPE. 

The  whole  is  supported  on  a  short,  stout  pillar  rising  from  the 
base,  O. 

LENSES    OF    THE    MICROSCOPE 

Fig.  2  shows  the  arrangement  of  lenses,  including  a  high- 
power  objective. 

The  objective,  A,  is  provided  with  one  simple  and  two  compound 
lenses.  The  lens,  B,  nearest  the  object,  and  the  one  upon  which 
the  magnifying  power  mainly  depends,  is  a  hemisphere  of  crown 
glass.  A  lens  of  such  form  possesses  both  chromatic  and  spherical 
aberration  in  high  degree.  These  faults  are  corrected  by  the  com- 
pound flint  and  crown  lenses,  C  and  D,  placed  above  the  hemi- 
spherical glass. 

The  eye -piece  consists  of  two  crown  glass,  plano-convex  lenses, 


LENSES    OF   THE   MICROSCOPE 


with  their  plane  surfaces  upward.  The  lower,  E,  is  known  as  the 
field -lens  ;  the  upper,  F,  as  the  eye -lens.  Eye -pieces  add  very 
materially  to  the  magnifying  power  of  the  instrument,  and  are 


FIG.  2.     DIAGRAM  SHOWING  THE  RELATION  OP 
THE  OBJECTIVE  TO  THE  EYE-PIECE. 

constructed  of  various  strengths  depending  upon  the  curvature  of 
the  lenses.  They  are  named  according  to  power,  A,  B,  C,  or  1,  2, 
and  3,  or  according  to  their  focal  distances.  The  medium  power 
is  more  commonly  employed. 

The  microscope  previously  described  stands,  with  the  draw- tube 


4  STUDENTS  HISTOLOGY 

in  place,  about  twelve  inches  high.  If  the  height  of  the  table 
upon  which  it  is  placed  and  the  chair  of  the  observer  be  in  a 
proper  relation,  no  discomfort  need  be  experienced  in  using  the 
microscope  in  the  vertical  position.  The  form  of  condenser 
invented  by  Abbe  may  be  placed  directly  below  the  stage  (Fig.  1,  K) . 
It  consists  of  two  or  three  lenses  combined  so  as  to  focus  the  rays 
coming  from  the  plane  mirror  upon  the  object.  The  condenser 
gives  a  very  intense  illumination  over  a  small  field,  and  is  adapted 
to  bacteriological  work,  where  a  high -power  oil -immersion  objective 
is  required.  An  oil -immersion  objective  is  a  specially  constructed 
system  of  lenses,  with  which  a  layer  of  thickened  oil  of  cedar  wood 
is  placed  between  the  lower  surface  of  the  objective  and  the  upper 
surface  of  the  glass  covering  the  object  under  examination.  The 
oil -immersion  lens  in  general  use  has  an  equivalent  focal  length 
of  one -twelfth  of  an  inch,  and  is  usually  designated  as  the  iV-inch 
oil -immersion.  For  similar  reasons,  the  low -power  is  a  f-  or 
f-inch,  and  the  ordinary  high-power  is  a  i-,  i-,  or  i-inch  objective, 
as  the  case  may  be.  The  condenser  is  not  necessary,  except  with 
the  high-power  oil-immersion  objective.  If  used  with  the  other 
objectives,  the  illumination  must  be  regulated  by  lowering  the 
condenser,  closing  the  diaphragm,  and  substituting  the  concave  for 
the  plane  mirror,  till  a  clear  and  satisfactory  picture  is  secured. 

ADJUSTMENT    OF    THE    MICROSCOPE 

The  microscope  should  be  placed  in  front  of  the  observer,  on  a 
table  of  such  height  that,  when  seated,  he  may,  by  slightly  inclin- 
ing the  head,  and  without  bending  the  body,  bring  the  eye  easily 
over  the  eye -piece.  The  slightest  straining  of  the  body  or  neck 
should  be  avoided.  The  light  should  always  be  taken  from  the 
side,  and  it  matters  little  which  side.  Clouds  or  clear  sky  serve  as 
the  best  source  of  light  for  our  present  work.  Always  avoid  direct 
sunlight.  If  artificial  illumination  be  employed — though  it  is  not 
advised  for  prolonged  investigation — a  small  coal -oil  flame  may  be 
tempered  by  blue  glass,  or  better  a  Welsbach  gas-burner  with  a 
blue  glass  globe,  or  an  incandescent  electric  light. 

ADJUSTMENT    FOR    ILLUMINATION 

It  will  be  observed  that  there  are  two  mirrors  in  the  circular 
frame  below  the  stage — one  plane  and  the  other  concave,  The 


ADJUSTMENT  FOR    FOCUS  O 

latter  will  be  employed  almost  exclusively  in  the  work  of  this 
volume,  and  its  curvature  is  such  that  parallel  rays,  impinging 
upon  its  surface,  are  focused  about  two  inches  from  the  mirror. 
It  will  also  be  noticed  that  the  bar,  carrying  the  mirror -fork,  may 
be  made  to  swing  the  mirror  from  side  to  side.  The  work  whieh 
we  are  about  to  undertake  is  of  such  a  character  as  to  require  the 
avoidance  of  oblique  illumination.  We  must,  therefore,  keep  our 
mirror -bar  strictly  in  the  vertical  position.  If — the  mirror -bar 
being  vertical — a  line  be  drawn  from  the  center  of  the  face  of  the 
mirror,  through  the  opening  (diaphragm)  in  the  stage,  passing  on 
through  the  objective,  and  so  continued  upward  through  the  body 
and  the  eye -piece,  such  a  line  would  pass  through  the  optical  axis. 
The  center  of  the  face  of  the  mirror  must  be  in  this  axis.  If, 
then,  having  gotten  the  mirror -bar  properly  fixed  once  for  all,  the 
light  from  the  adjacent  right  or  left  hand  window  impinges  upon 
the  concave  surface  of  the  mirror,  and  the  latter  be  properly 
inclined,  the  rays  will  pass  through  the  diaphragm  in  the  stage, 
and  become  focused  a  little  above  the  same.  The  light  rays  will 
afterward  diverge,  enter  the  objective,  and  finally  reach  the  eye  of 
the  observer. 

The  field  of  view  (as  the  area  seen  in  the  microscope  is  termed) 
we  will  suppose  to  have  been  properly  illuminated — and  by  this  we 
mean  that  it  presents  us  a  clear,  evenly  lighted  area.  Turn  all  the 
factors  spoken  of  out  of  adjustment,  and  proceed  to  readjust. 
Observe  that,  if  the  mirror  be  turned— not  swung— slightly  out  of 
proper  position,  one  side  of  the  field  will  appear  dim  or  cloudy. 
This  must  be  corrected,  and  the  student  must  practice  until  this 
adjustment  becomes  easy  of  accomplishment.  Then  proceed  to  the 

ADJUSTMENT    FOR    FOCUS 

Swing  the  low -power  objective  into  use,  and  rack  the  tube  up 
or  down  until  it  is  about  one -fourth  of  an  inch  from  the  stage. 
Place  a  mounted  object  upon  the  stage  (a  stained  section  of 
some  organ— say  kidney— will  be  preferable).  Examine  the  field 
through  the  eye -piece,  and  it  will  be  found  obscured  by  the  stained 
object,  and  perhaps  a  dim  notion  of  figure  may  be  made  out. 
Rack  the  body  up  carefully,  watching  the  effect.  The  image 
becomes  more  and  more  distinct  until,  at  a  certain  point,  the  best 
effect  is  secured.  The  object  is  in  focus. 

Note  carefully  the  distance  between  the  object  and  the  objective 


6  STUDENTS    HISTOLOGY 

(with  the  low -power  this  will  be  less  than  one -half  of  an  inch), 
and  hereafter  you  will  be  able  to  focus  more  quickly. 

Having  observed  the  details  of  structure  as  shown  with  the  low- 
power,  swing  the  high -power  into  use.  Rack  the  tube  down  until 
the  objective  is  very  near  to  the  glass  covering  the  object.  The 
field  is  much  obscured.  Watching  the  effect  through  the  eye- 
piece, rack  the  tube  up  with  great  care  until  the  image  appears 
sharp.  Note  the  distance  with  this  objective,  as  before  with  the 
low -power,  from  one -twelfth  of  an  inch  to  considerably  less. 
Then  endeavor,  by  slight  alterations  in  the  inclination  of  the 
mirror,  to  increase  the  illumination.  Turn  the  diaphragm  so  that 
the  light  passes  through  a  small  opening,  and  note  the  improve- 
ment in  definition.  The  rule  is:  The  higher  the  power,  the  smaller 
the  diaphragm. 

You  have  doubtless  observed,  before  this,  that  you  cannot  con- 
trol the  focusing  as  easily  as  when  the  low -power  was  in  use. 
Slight  movements  of  the  rack -work  produce  marked  changes  in 
definition;  and  it  is  difficult,  with  the  coarse  adjustment  alone,  to 
make  as  slight  movements  as  you  may  desire.  Recourse  must  be 
had  to  the  fine  adjustment. 

Place  the  tip  of  the  forefinger  (either)  upon  the  milled  head  of 
the  fine  focusing -screw,  and  the  ball  of  the  thumb  against  its 
side,  so  that  the  hand  is  in  an  easy  position.  By  a  little  lateral 
pressure  the  milled  head  may  be  turned  slightly  either  way.  Note 
the  effect  on  the  image.  You  thus  have  the  focusing  under  the 
most  perfect  control. 

Remember  that  the  fine  adjustment  is  only  necessary  with  high- 
powers,  and  then  only  after  the  image  has  been  found  with  the 
coarse  adjustment. 

METHOD     IN     OBSERVATION 

The  study  of  objects  under  the  microscope  should  be  conducted 
with  order  and  method. 

The  body  being  in  the  position  before  advised,  so  that  the 
sitting  may  be  prolonged  without  fatigue,  let  one  hand  be  occupied 
in  the  maintenance  of  the  focal  adjustment.  It  will  be  found, 
however  flat  an  object  may  seem  to  the  unaided  eye,  that  as  it  is 
moved  so  as  to  present  different  areas  for  examination  (and  with 
the  higher- powers  only  a  small  area  can  be  seen  at  once),  constant 
manipulation  with  the  fine  adjustment  will  be  required.  It  will 


MAGNIFYING    POWER    AND    MEASUREMENT   OF   OBJECTS         1 

also  be  found  that  even  the  various  parts  of  a  simple  histological 
element — like  a  cell — cannot  be  seen  sharply  with  a  single  focal 
adjustment.  The  forefinger  and  thumb  of  one  hand  must  be  kept 
constantly  on  the  milled  head  of  the  fine  focusing -screw.  Sup- 
posing the  light  to  be  011  our  right,  we  devote  the  right  hand  to 
the  focusing. 

The  left  hand  will  be  engaged  with  the  glass  slip  upon  which 
the  object  has  been  mounted.  The  forearm  resting  upon  the  table, 
let  the  thumb  and  forefinger  rest  on  the  left  upper  side  of  the 
stage,  just  touching  the  edges  of  the  glass  slip.  The  slightest 
pressure  will  then  enable  you  to  move  the  slip  smoothly,  steadily, 
and  delicately. 

Proceed  to  examine  the  object  with  method.  Suppose  a  section 
of  some  tissue  to  be  under  examination — say  one -fourth  of  an  inch 
square.  With  the  high -power  you  will  be  able  to  see  only  a  small 
fraction  of  the  area  at  once.  Commence  at  one  corner  to  observe, 
and,  with  the  left  hand,  move  tfre  object  slowly  in  successive 
parallel  lines,  preserving  the  focus  with  the  right  hand,  until  the 
whole  area  of  the  section  has  been  traversed. 

Practice  will  soon  establish  perfect  co-ordination  of  the  move- 
ments involved,  and  will  result  in  the  ability  to  work  with  ease, 
celerity,  and  profit. 

CONSERVATION    OF    THE    EYESIGHT 

The  beginner  should  not  become  accustomed  to  the  use  of  one 
eye  alone,  or  of  closing  either  in  microscopical  work.  It  will 
require  but  little  practice  to  use  the  eyes  alternately,  and  the 
retinal  image  of  the  unemployed  eye  will  soon  be  ignored  and 
unnoticed. 

MAGNIFYING    POWER    AND    MEASUREMENT    OF    OBJECTS 

The  microscope  is  not,  as  the  beginner  usually  supposes,  to  be 
valued  according  to  its  power  of  enlargement  or  magnification, 
but  rather  according  to  the  clearness  and  sharpness  of  the 
image  afforded. 

Magnifying  power  is  generally  expressed  in  diameters.  A 
certain  area  is  by  the  instrument  made  to  appear,  say,  ten  times 
as  large  as  it  appears  to  the  naked  eye.  This  object,  then,  has  its 
apparent  area  increased  one  hundred  times;  but  reference  is  made 


8 


STUDENTS  HISTOLOGY 


in  describing  such  phenomena  only  to  amplification  in  a  single 
direction.  The  diameter  of  the  object  under  examination  has  been 
increased  ten  times  and  would  be  expressed  by  prefixing  the  sign 
of  multiplication:  e.g.,  X  10. 

A  convenient  unit  of  approximate  measurement  for  the  histolo- 
gist  is  the  apparent  size  of  a  human  red  blood -corpuscle  with  a 
given  objective.  Thirty -two  hundred  corpuscles,  placed  side  by 
side,  would  measure  one  inch;  or,  we  say,  the  diameter  of  a  single 
corpuscle  is  the  thirty -two -hundredth  of  an  inch.  After  consider- 
able practice,  you  will  become  accustomed  to  the  apparent  size  of 
this  object  with  a  certain  objective  and  eye -piece.  This  will  aid  in 
an  approximate  measurement  of  objects  by  comparison,  and  will 
further  give  the  magnifying  power  of  the  microscope.  If  a  cor- 
puscle appears  magnified  to  one  inch  in  diameter,  it  is  evident  that 
the  instrument  magnifies  thirty -two  hundred  times.  Should  the 


1 

Inches. 

2                                       3 

4 

I  1 

1  II  1  1  1  1  11 

1  1  1 

1  1 

1  1 

1 

MM 

1  1  1 

I  i 

MM 

II  II  II  1 

1    1    1    II 

1  1 

1  i  1  II  1 

Illl 

Illllllll 

Illl1 

U 

! 

MM 

|| 

lIlMI 

mi 

mi 

Illl 

Illl   IIU 

3 


10 


4567 

Centimeters. 
FIG.  3.    ENGLISH  AND  METRIC  SCALES. 

diameter  appear  one -quarter  of  an  inch,  the  power  is  eight  hun- 
dred ;  one-eighth  of  an  inch,  four  hundred,  etc.  The  instrument 
which  we  have  heretofore  described,  with  the  high- power  in  use  and 
the  tube  withdrawn,  will  present  the  corpuscle  as  averaging  very 
nearly  one -eighth  of  an  inch  in  diameter — X  400.  While  this 
gives  a  gross  idea  of  amplification,  the  method  will  often  prove 
to  be  inaccurate  because  of  individual  errors  in  the  estimation  of 
proportions. 

Measurements  made  with  the  microscope  are  usually  based  on 
the  metric  system.  The  unit  taken  is  one -thousandth  part  of  a 
millimeter,  or  a  micro -millimeter,  called  also  a  micron,  for  which 
the  Greek  letter  p  has  been  taken  as  the  symbol.  Roughly,  1  p 
equals  25000  inch.  A  convenient  instrument  for  measuring  is  an 
eye -piece  micrometer,  a  ruled  disk  of  glass,  which  may  be  placed 
within  the  eye -piece,  and  the  diameters  of  objects  read  off  by 
means  of  the  ruled  scale. 


PREPARATION   OF   TISSUES  9 

SKETCHING    FROM    THE    MICROSCOPE 

Let  us  most  emphatically  urge  the  practice  of  sketching  in 
connection  with  microscopy.  "I  am  no  artist,"  or  "I  have  no  skill 
in  drawing,"  is  often  the  reply  to  our  advice  in  this  matter.  We- 
then  suggest  that  no  special  skill  is  needed  to  begin  with,  only 
patience  and  a  dogged  determination  to  succeed.  The  pictures  in 
the  microscopic  field  have  no  perspective,  and  may  be  reproduced 
in  outline  merely.  Begin  with  simple  tissues,  reserving  intricate 
detail  until  a  short  period  of  practice  gives  the  technique  needed. 
We  do  not  recommend  the  camera  lucida,  as  our  experience  strongly 
impresses  us  with  this  as  a  fact,  that  he  who  cannot  sketch 
without  a  camera  will  never  sketch  with  one.  Pencil  drawings 
may  be  very  effectively  colored  with  our  staining  fluids,  diluted 
if  necessary. 


PREPARATION   OF   TISSUES   FOR    MICROSCOPICAL   PURPOSES 
TISSUES     ARE     STUDIED     BY    TRANSMITTED     LIGHT 

The  microscopical  study  of  both  normal  and  pathological  tis- 
sues is  invariably  conducted  by  the  aid  of  transmitted  light. 

Tissues,  if  not  naturally  of  sufficient  delicacy  to  transmit  light, 
must  in  some  way  be  made  translucent. 

Delicate  tissues  like  omenta,  desquamating  epithelia,  fluids 
containing  morphological  elements,  certain  fibers,  etc.,  are  suffi- 
ciently diaphanous,  and  require  no  preparation.  Such  objects  are 
simply  placed  upon  the  glass  slip,  a  drop  of  some  liquid  added, 
and,  when  protected  by  a  thin  covering  glass,  are  ready  for  the 
stage  of  the  microscope. 

PREPARATION    BY    TEASING 

The  elements  of  structures  mainly  fibrous — e.g.,  muscle,  nerve, 
ligament,  etc. — are  well  studied  after  a  process  of  separation,  by 
means  of  needles,  known  as  teasing.  A  minute  fragment  of  the 
organ  or  part,  having  been  isolated  by  the  knife  or  scissors,  is 
placed  upon  a  glass  slip,  and  a  drop  of  some  fluid  which  will  not 
alter  the  tissue  added.  Stout  sewing -needles,  stuck  in  slender 
wood  handles,  are  commonly  employed  in  the  teasing  process. 


10  STUDENTS  HISTOLOGY 

The   separation  of   tissues   is   frequently  facilitated  by  means  of 
dissociating  fluids,  which  remove  the  cement  substance. 

SECTION     CUTTING 

After  having  become  familiar  with  the  various  elementary 
structures  of  animal  tissues,  we  proceed  to  the  study  of  their 
relation  to  organs. 

As  the  teasing  process  is  not  available  with  such  complicated 
structures  as  lung,  liver,  kidney,  brain,  etc.,  we  resort  to  methods 
of  slicing — i.e.,  section  cutting. 

Sections  must  be  made  of  extreme  tenuity,  in  order  that  the 
naturally  opaque  structures  may  be  illuminated  ~by  transmitted 
light.  This  becomes  an  easy  matter  with  such  tissues  as  cartilage; 
but  some,  like  bone,  are  much  too  hard  to  admit  of  cutting,  and 
others  are  as  much  too  soft  ;  so  that  while  certain  tissues  must  be 
softened,  the  majority  must  be  hardened.  Fortunately,  both  of 
these  conditions  may  be  secured  without  in  any  way  altering  the 
appearance  or  relations  of  the  structures.  Hardening  processes, 
from  necessity,  become  a  prominent  feature  in  histological  work ; 
but  we  propose  here  to  indicate  some  of  the  more  useful  methods 
of  section  cutting,  reserving  the  hardening  processes  for  another 
place. 

FREE-HAND    SECTION    CUTTING 

The  students,  when  ready  for  this  work,  are  provided  with  some 
tissue  which  has  been  previously  hardened.  We  will  take,  for 
example,  a  piece  of  liver  which  has  been  rendered  sufficiently  firm 
for  our  work  by  immersion  in  alcohol,  and  proceed  to  direct  the 
steps  in  obtaining  suitable  sections  by  the  simple  free-hand 
method. 

We  wish  to  strongly  emphasize  the  importance  of  this  mode  of 
cutting.  A  moderate  amount  of  practice  will  render  the  micros- 
copist  independent  of  all  appliances,  save  those  of  the  most  simple 
character  and  which  are  always  obtainable. 

An  ordinary  razor  with  keen  edge,  and  a  shallow  dish,  prefer- 
ably a  saucer,  partly  filled  with  alcohol,  are  required.  The  razor 
best  adapted  to  the  work  is  concave  on  one  side  (the  upper  side,  as 
seen  in  Fig.,  4)  and  nearly  flat  on  the  other,  although  this  is 
largely  a  matter  of  personal  preference. 

Fig.  4  indicates  the  proper  position  of  the  hands  in  commenc- 


FREE -H AS 'D    SECTION   CUTTING  11 

ing  the  cut.  The  beginner  must  follow  directions  closely  until  he 
acquires  skill  with  practice.  The  student  should  be  seated  at  a 
table  of  such  height  as  to  afford  a  convenient  rest  for  the  fore- 
arms. A  small  piece  of  tissue  is  held  between  the  thumb  and 
forefinger  of  the  left  hand,  so  that  it  projects  slightly  above  both 
(In  the  cut,  a  cube  of  tissue  too  small  to  handle  in  this  way  has 
been  cemented  to  a  cork  with  paraffin  in  the  manner  hereafter 
described,  and  the  cork  held  as  just  mentioned.)  The  hand  carry- 
ing the  tissue  is  held  over  the  saucer  of  alcohol.  The  razor,  held 
lightly  in  the  right  hand,  as  seen  in  the  figure,  is,  previous  to 


FIG.  4.     FREE-HAND  SECTION  CUTTING. 

making  every  cut,  dipped  flatwise  into  the  alcohol  so  as  to  wet  it 
thoroughly,  and  is  then  lifted  horizontally,  carrying  several  drops— 
perhaps  half  a  drachm— of  the  fluid  on  the  concave  upper  surface. 
The  alcohol  serves  to  prevent  the  section  from  adhering  to  the 
knife,  and  to  moisten  the  tissue.  If  allowed  to  become  dry,  the 
latter  would  be  ruined  by  alterations  of  structure. 

Now,  as  to  the  manner  of  moving  the  knife.  Resting  the  under 
surface  upon  the  forefinger  for  steadiness,  bring  the  edge  of  the 
blade  nearest  the  heel  to  the  margin  of  the  tissue  furthest  from 
you.  Then,  entering  the  edge  just  below  the  upper  surface  of 
the  tissue,  with  a  light  but  steady  hold  draw  the  knife  toward  the 
right,  at  the  same  time  advancing  the  edge  toward  the  body.  This 
passes  the  knife  through  the  tissue  diagonally,  and  leaves  the 
upper  surface  of  the  latter  perfectly  flat  or  level.  Remove  the 


12 


STUDENTS  HISTOLOGY 


piece  which  has  been  cut,  and  repeat  the  operation.  Do  not 
attempt  to  cut  large  or  very  thin  sections  at  first.  A  minute 
fragment,  if  thin,  is  valuable. 

As  the  razor  is  drawn  through  the  tissue,  the  section  floats  in 
the  alcohol;  depress  the  point  of  the  knife,  and  the  section  will 
slide  into  the  saucer  of  spirit,  and  thus  prevent  its  injury.  If  it 
does  not  leave  the  knife  readily,  brush  it  along  with  a  camel' s- 
hair  pencil  which  has  been  well  wet  with  the  alcohol. 

Proceed  in  the  above  manner  until  the  tissue  is  exhausted, 
when  you  will  have  a  great  number  of  sections,  large  and  small, 


FIG.  5.     STIRLING'S  MICROTOME. 

thick  and  thin.  Selecting  the  thinnest,  lift  them  carefully  with  a 
needle,  one  at  a  time,  into  a  small,  wide -mouthed  bottle  of  alcohol; 
cork  and  label  for  future  use. 

When  the  work  is  finished,  and  before  the  spirit  has  evaporated 
from  your  fingers — it  is  impossible  to  avoid  wetting  the  skin  more 
or  less— wash  them  thoroughly  and  wipe  dry.  This  saves  the 
roughening  of  the  hands  which  is  apt  to  result  when  alcohol  has 
been  allowed  to  dry  upon  them  repeatedly. 

SECTION    CUTTING    WITH    THE     STIRLING    MICROTOME 

Of  the  numerous  mechanical  aids  to  section  cutting,  we  shall 
mention  only  two  or  three.  One  of  the  earlier  and  better  known 


SECTION   CUTTING    WITH    THE    MICROTOME  13 

instruments  is  seen  in  Fig.  5.  The  Stirling  microtome  consists 
essentially  of  a  short  brass  tube,  into  which  the  tissue  is  fixed 
either  by  pressure  or  by  imbedding  in  wax.  A  screw  enters  below, 
which,  acting  on  a  plug,  raises  the  contents  of  the  tube.  As  the 
material  to  be  cut  is  raised  from  time  to  time  by  the  screw,  it 
appears  above  the  plate  which  surrounds  the  top  of  the  tube. 
This  plate  steadies  and  guides  the  razor ;  and  it  is  evident  that 
more  uniform  sections  may  be  cut  with  this  little  apparatus  than 
'would  be  possible  with  nothing  to  support  the  knife,  or  to  regulate 
thickness,  beyond  the  unaided  skill,  of  the  operator. 

Much  depends  upon  the  manner  in  which  the  material  is  fixed 
in  the  tube  or  well  of  the  microtome.  If  the  tissue  be  of  a  solid 
character,  like  liver,  kidney,  spleen,  many  tumors,  etc.,  it  may  be 
surrounded  with  some  carefully  fitted  pieces  of  elder-pith,*  carrot, 


FIG.  6.     MANNER  OF  CUTTING  AND  ARRANGING  PIECES  OF  PITH,  TURNIP,  ETC.,  FOR 
SUPPORTING  HARDENED  TISSUE  IN  THE  WELL  OF  A  MICROTOME. 

etc.,  and  the  whole  pressed  evenly  and  quite  firmly  into  the  well. 
A  small  piece  of  tissue  which,  by  cutting,  can  be  made  somewhat 
cubical  in  shape,  may  be  surrounded  by  slabs  of  pith,  carrot,  or 
turnip,  shaped  as  in  Fig.  6.  Indeed,  the  fragments  of  imbedding 
material  can  be  shaped  so  as  to  fit  tissue  of  almost  any  form. 
Before  the  whole  is  pressed  into  the  well  of  the  microtome,  the 
bottom,  against  which  the  brass  plug  fits,  should  be  cut  off  square. 
The  wax  method  of  imbedding  is  employed  with  tissues  such  as 
brain,  lung,  soft  tumors,  etc.,  which  might  be  injured  by  the 
previous  treatment.  To  three  parts  of  paraffin  wax  (a  paraffin 
candle  answers  perfectly)  add  one  part  of  vaselin,  and  heat  until 
thoroughly  mixed.  The  microtome  having  been  previously  warmed 
— standing  upright — is  filled  with  the  imbedding  mixture.  The 


"The  pith  from  the  young  shoots  of  Ailantus  glandulosus  (improperly  called  "Alanthus"), 
gathered  in  early  autumn,  is  the  best  material  for  this  method  of  imbedding  with  which  I  am. 
acquainted.  The  wood  is  easily  cut  from  the  pith,  and  the  latter  is  very  large  and  firm. 


14 


STUDENTS    HISTOLOGY 


piece  of  tissue  is  then  carefully  wiped  dry  with  the  blotting-paper, 
and,  just  as  the  imbedding  begins  to  congeal  around  the  edges,  is 
pressed  below  the  surface  with  a  needle  and  held  until  the  cool 
mixture  fixes  it  in  position.  The  whole  is  now  allowed  to  become 
thoroughly  cold.  By  turning  the  screw  the  plug  of  wax  is  raised; 


FIG.  7.     METHOD  OF  CUTTING  SECTIONS  WITH  THE  STIRLING  MICROTOME. 

and  it  must  be  gradually  cut  away,  by  sliding  the  knife  across  the 
plate,  until  the  upper  part  of  the  tissue  appears. 

Before  commencing  to  cut  sections — however  the  tissue  may 
have  been  imbedded — provide  yourself  with  a  saucer  of  alcohol  and 
a  camel's -hair  pencil.  Having  wet  the  knife,  turn  the  screw  so 
that  the  tissue,  with  its  imbedding,  appears  slightly  above  the 


FIG.  8.    THOMA  MICROTOME. 

plate  of  the  microtome,  and  then,  resting  the  blade  of  the  razor  on 
the  plate  (vide  Fig.  7),  make  the  cut  precisely  as  in  free-hand 
cutting.  The  section  is  then  brushed  off  into  the  saucer,  the 
screw  turned  up  slightly,  the  razor  wet,  and  a  second  cut  made. 
These  steps  are  repeated  until  the  required  number  of  sections  has 
been  obtained. 


SECTION   CUTTING    WITH   THE    MICROTOME 


15 


The  imbedding  material  will  separate  from  the  cuts  as  they 
are  floated  in  the  alcohol.  They  may  now  be  selected,  lifted 
with  the  needle  into  clean  spirit,  and  preserved,  as  before  indi- 
cated, for  future  operations.- 

The  finest  section  cutting  can  only  be  done  with  one  of  the 
more  elaborate  and  expensive  microtomes  (Figs.  8  and  9).  Each 
of  these  instruments  consists  of  a  heavy  sliding  knife -carrier, 
which  moves  on  a  level  and  with  great  precision,  and  of  a  device 


FIG.  9.    SCHANZE  MICROTOME. 

(screw  or  inclined  plane)  for  elevating  the  object  that  is  cut  the 
desired  distance  after  each  excursion  of  the  knife.  The  distance 
that  the  object  is  raised  is,  of  course,  the  thickness  of  the  sec- 
tion. Such  microtomes  are  especially  adapted  to  cutting  frozen 
tissues  or  those  imbedded  in  celloidin,  but  they  may  be  used  with 
paraffin  imbedding.  The  Minot  microtome,  which  is  intended  for 
cutting  objects  in  paraffin,  is  preferable  for  the  latter  purpose, 
especially  if  a  number  of  sections  are  to  be  kept  in  the  order  in 
which  they  were  cut, — "serial  sections." 


16 


STUDENTS    HISTOLOGY 


SHARPENING    KNIVES 

In  the  majority  of  instances  of  failure  to  produce  suitable  sec- 
tions for  microscopical  work,  the  cause  can  be  set  down  to  dull 
knives,  and  we  would  urge  the  student  to  practice  honing  until  able 
to  put  cutting  instruments  in  good  condition.  If  he  will  but  start 
properly,  success  is  sure.  Nine -tenths  of  the  microtomes  are  pur- 
chased because  of  failure  in  free-hand  work  with  a  dull  knife  ;  but 
no  advantage  will  ~be  gained  by  a  machine,  if  the  student  be  incapa- 
ble of  keeping  the  knife  up  to  a  proper  degree  of  keenness. 

A  knife  is  a  wedge,  and  for  our  purpose  the  edge  must  be  of 
more  than  microscopical  tenuity — it  being  impossible  with  the 
microscope  to  discover  notches  and  nicks  if  properly  sharpened. 

It  is  impossible  to  secure  the  best  results  with  indifferent  tools. 


FIGS.  10  AND  11.     METHOD  OF  HONING. 


The  knife  is  first  brought  with  its  heel  in  the  position  shown  at  A,  Fig.  10.  It  is  then  drawn 
forward  as  indicated  by  the  curved  dotted  line  until,  at  the  end  of  the  stroke,  the  position  C 
is  attained.  Fig.  11  indicates  the  method  of  turning  the  blade  before  reversing  and  between 
each  stroke. 

The  knife  should  be  hard  enough  to  support  an  edge,  but  not  so 
hard  as  to  be  brittle.  The  proper  temper  is  about  that  given  a 
good  razor. 

We  need  at  least  two  hones — one  comparatively  coarse,  for 
removing  slight  nicks,  and  another  for  finishing.  The  first  part  of 
the  work  is  best  done  by  means  of  a  sort  of  artificial  hone  made 
of  ground  corundum.  These  are  kept  in  stock  by  dealers  in 
mechanics'  supplies,  of  great  variety 'in  size  and  fineness.  For 
razors  a  "00"  corundum  slip  will  best  answer.  This  will  very 


SHARPENING    KNIVES  17 

rapidly  remove  the  inequalities  from  an  exceedingly  dull  razor.  A 
Turkish  hone  will  be  best  for.  finishing.  For  large  knives  we 
use  a  third  very  soft  and  fine  stone. 

Let  the  corundum  slip  be  placed  on  a  level  support  (or  be 
fitted  into  a  block  like  the  carpenter's  oil-stone),  and  cover  the 
surface  liberally  with  water.*  The  hones  should  always  be  worked 
wet.  Place  the  knife  flat  on  the  stone  near  the  right  hand,  as  at 

A,  Fig.  10.     Draw  steadily  in  the  direction  of  the  curved  dotted 
line — i.e.,  from  right  to  left — holding  the  blade  firmly  on  the  stone, 

B,  with  slight  pressure  until  the  position  C  is  attained.     Rotate  the 
razor  on  its  back — vide  Fig.  11 — so  as  so  bring  the  other  side  on 
the  stone,  and  draw  from  left  to  right.     Observe  that  as  the  knife 
is  drawn  from  side  to  side  (the  edge  invariably  looking  toward  the 
draw)  it  is  always  worked   from  heel  to  point.     The  amount  of 
pressure  may  be  proportioned  to  the  condition  of  the  edge.     If  it 
be  badly  nicked,  considerable  pressure  may  be  employed  ;   while,  as 
it  approaches  keenness,  the  pressure  is  to  be  lessened,  until  the 
weight  of  the  blade  alone  gives  sufficient  friction. 

Repeat  the  process  fifteen  or  twenty  times,  and  examine  the 
blade.  If  the  nicks  are  yet  visible,  continue  honing  until  they  can 
no  longer  be  seen.  Then  draw  the  edge  across  the  thumb-nail. 
Do  this  lightly,  and  the  sense  of  touch  will  reveal  indentions 
which  the  eye  failed  to  recognize.  Continue  the  use  of  the  coarse 
stone  until  the  edge  is  perfect,  so  far  as  the  thumb-nail  test 
indicates. 

The  knife  is  then  to  be  carefully  wiped,  so  as  to  remove  any 
coarse  particles  of  corundum,  and  applied  to  the  wetted  Turkish 
hone  with  precisely  the  same  motions  as  were  employed  in  the  first 
process.  After  a  dozen  or  two  strokes,  examine  the  edge  by 
applying  the  palmar  aspect  of  the  thumb,  with  repeated  light 
touches,  from  heel  to  point.  This  looks  slightly  dangerous  to 
the  novice,  but  it  is  an  excellent  method  of  determining  the  con- 
dition. Of  course  actual  trial  with  a  piece  of  hardened  tissue  is 
the  best  test. 

A  fine  water -stone  or  the  Belgian  hone  of  the  hardware  shops 
may  be  used  instead  of  the  corundum  hone. 

It  is  best  to  finish  with  stropping,  and  often  a  knife  may  be 
sharpened  by  stropping  alone.  The  leather  of  the  strop  should 
be  glued  to  a  support  of  wood  to  keep  it  flat.  The  movement  is 

*A  few  drops  of  glycerin  added  to  the  water  retard  evaporation,  and  appear  to  keep  the 
surface  of  the  hone  in  good  condition. 


18 


STUDENTS    HISTOLOGY 


the  reverse  of  that  employed  for  honing.  The  motion  is  from  toe 
to  heel,  the  back  of  the  knife  preceding  the  edge.  Fig.  10,  with 
the  arrow  reversed,  illustrates  the  movement. 


SUPPORTING    TISSUES    FOR    CUTTING 

Frequently  small  bits  of  tissue  are  required  to  be  cut — pieces 
too  small  to  be  held  with  the  fingers.     We  are  in  the  habit  of 


FIG.  12.     INSTRUMENT  FOR  SOLDERING  TISSUE  TO  CORK  SUPPORTS  WITH  PARAFFIN. 

It  consists  of  an  awl-handle  of  wood  into  which  a  short  piece  of  wire,  preferably  copper,  is 
driven  and  bent  as  shown. 

cementing  such  tissues  into  a  hole  in  a  bit  of  ailantus-  or  elder - 
pith,  when  the  whole  may  be  cut  as  one  mass.  Tissue  is  fre- 
quently cemented  to  cork  for  convenience  of  holding  in  free-hand 


FIG.  13.     METHOD  OF  CEMENTING  TISSUE  TO  A  CORK  SUPPORT  WITH  PARAFFIN. 


cutting ;    or  the  cork  may  be  held  in  the  vise  of  the  microtome. 
The  edge  of  the  knife  should  not  be  allowed  to  touch  the  cork. 
Fig..  12  shows  a  simple  little  instrument,  very  convenient  for 


THE    FREEZING    MICROTOME 


19 


using  paraffin  as  a  cement.  A  piece  of  stout  copper  or  brass  wire 
is  bent  as  indicated,  pointed,  and  driven  into  an  ordinary  awl- 
handle.  Paraffin  wax  possesses  the  very  valuable  property  of 
remaining  solid  at  ordinary  temperatures,  not  cracking  in  the  cold, 
of  winter  nor  softening  in  summer.  It  is  unaltered  by  most  re- 
agents, is  easily  rendered  fluid,  and  quickly  solidifies.  As  a 
cement,  it  is  invaluable  to  the  microscopical  technologist. 

Fig.  13  indicates  the  method  of  cementing  a  piece  of  tissue  to  a 
cork  or  other  support.  The  tissue  having  been  properly  placed, 
the  wire  tool  is  heated  for  a  moment  in  the  alcohol  flame,  and  then 


FIG.  14.     CATHCART'S  ETHER  FREEZING  MICROTOME. 

touched  to  a  cake  of  paraffin.  The  paraffin  is  melted  in  the 
vicinity  of  the  hot  wire,  a  drop  adheres  to  the  latter  and  is  carried 
to  the  edge  of  the  tissue.  In  the  cut  the  wire  tool  is  seen  in  the 
position  necessary  for  cementing  one  edge.  The  wire  being 
removed,  the  wax  immediately  cools  and  becomes  solid.  The  other 
sides  are  afterward  cemented  in  like  manner.  The  whole  is  done 
in  less  time  than  is  necessary  to  the  description  of  the  process. 


THE    FREEZING    MICROTOME 


After  freezing  a  piece  of  tissue,  sections  may  be  cut  without  the 
delay  required  for  imbedding  in  paraffin  or  celloidin.  Fresh  tissues 
may  be  used,  or  those  hardened  by  some  of  the  various  fixing 


20  STUDENTS    HISTOLOGY 

fluids,  preferably  formaldehyde,  may  be  taken.  Small  pieces  that 
have  been  hardened  for  a  few  hours  in  formaldehyde  may  be  cut 
very  thin  after  freezing,  and  this  plan  is  most  useful  in  pathological 
work.  Sections  of  fresh  tissues  may  be  examined  with  the  micro- 
scope directly,  or  they  may  be  placed  in  formaldehyde,  and  after- 
wards stained  and  mounted  as  directed  in  the  succeeding  pages. 
Sections  of  hardened  tissues  may  be  stained  and  mounted  in 
balsam. 

Freezing  of  the  specimen  is  done  upon  a  metal  box  or  plate, 
which  may  be  attached  to  the  ordinary  microtome.  Microtomes 
designed  especially  for  freezing  are  also  made  (Fig.  14).  Freezing 
is  best  accomplished  by  the  escaping  stream  of  carbon  dioxide  gas, 
derived  from  a  cylinder  of  the  compressed  gas.  An  ether -spray 
may  be  used  for  the  same  purpose,  or  the  water  running  from  a 
salt  and  ice  freezing  mixture  through  a  small  metal  case  which  may 
be  placed  on  the  microtome.  The  pieces  of  tissue  should  be  not 
more  than  five  millimeters  thick. 


FIXING    OR   HARDENING    FLUIDS 

We  have  already  seen  that  most  animal  tissues  are  unsuitable 
for  the  production  of  thin  sections  until  hardened. 

It  is  also  a  fact,  paradoxical  though  it  may  seem,  that  fresh 
tissues  do  not  present  truthful  appearances  of  structural  elements. 
The  old -school  histologists  insisted  upon  the  presentation  of  struc- 
tures unaltered  by  chemical  substances,  while  the  modern  worker 
has  discarded  such  tissue  with  very  few  exceptions.  Many  descrip- 
tions for  structure  and  growth,  the  result  of  study  upon  fresh 
material,  have  been  proved  by  later  methods  grossly  inaccurate. 

It  is  impossible  to  remove  tissues  from  the  living  animal  and  to 
subject  them  to  microscopical  observation  without,  at  the  same 
time,  exposing  them  to  such  radical  changes  of  environment  as  to 
produce  structural  alterations.  Certain  tissues  presenting  in  the 
living  condition  stellate  cells  with  the  most  delicate,  though  well- 
defined,  branching  processes,  when  removed  from  contact  with  the 
body,  however  expeditiously,  afford  no  hint  of  anything  resem- 
bling such  elements,  as  they  are  quickly  reduced  to  simple 
spherical  outlines. 

In  short,  it  is  impossible  to  study  fresh  material,  as  such,  with- 
out constant  danger  of  erroneous  conclusions,  as  retrograde  altera- 
tions of  structure  commence  with  surprising  rapidity  the  moment 


ALCOHOL    HARDENING  21 

a  part  is  severed  from  the  influences  which  control  the  complete 
organism. 

From  what  has  been  said,  we  appreciate  the  necessity  of  agents 
which,  when  applied  to  portions  freshly  removed  from  the  animal, 
or  even  before  removal,  shall  instantly  stop  all  physiological  pro- 
cesses and  retain  the  elements  in  permanent  fixity. 

Very  much  of  the  human  structure  which  is  available  will  be 
secured  only  after  functional  activities  have  long  ceased,  and  the 
structure  essentially  altered.  We  are,  therefore,  compelled  to 
resort  to  the  use  of  material  from  the  lower  animals  in  very  many 
instances. 

ALCOHOL     HARDENING 

The  tissue,  whatever  process  may  be  in  contemplation,  having 
been  removed  from  the  body  as  quickly  after  death  as  possible, 
should,  with  a  sharp  scalpel,  be  divided  into  small  pieces.  Of  the 
more  solid  organs,  pieces  not  more  than  one -half  to  one  centimeter 
thick  will  be  sufficiently  small,  and  they  will  harden  rapidly.  The 
smaller  the  pieces  and  the  larger  the  quantity  of  hardening  fluid, 
the  more  quickly  will  the  process  be  completed.  The  volume  of 
fluid  should  exceed  that  of  the  tissue  at  least  twenty  times.  Wide- 
mouthed,  well  stoppered  bottles,  from  one  ounce  to  a  pint,  or  even 
larger,  are  best,  and  they  should  be  carefully  labelled  and  kept  in 
a  cool  place,  with  occasional  agitation. 

Quick  Method. — A  piece  of  any  solid  organ,  say  liver,  spleen, 
pancreas,  kidney,  uterus,  lymph -node,  etc.,  not  more  than  one -half 
centimeter  thick,  may  be  perfectly  hardened  in  twelve  hours  by 
immersion  in  one  ounce  of  ninety -five  per  cent,  alcohol.  No  more 
should  be  thus  prepared  than  is  to  be  cut  within  twenty -four 
hours,  on  account  of  the  shrinkage  which  results  after  the  pro- 
longed immersion  of  solid  structures  in  strong  spirit. 

After  the  tissue  has  been  one  hour  in  the  above,  it  may  be 
hardened  in  one  or  two  hours  more  if  transferred  to  absolute 
alcohol.  This  method  is  of  frequent  advantage  in  pathological 
histology. 

Ordinary  Method. — Generally  it  is  better  to  place  the  pieces  of 
tissue  first  in  eighty  per  cent,  alcohol,  and  to  transfer  them  after  a 
few  hours  to  ninety -five  per  cent,  alcohol,  in  which  the  hardening 
is  completed.  In  this  manner  the  shrinkage  and  the  extreme 
hardening  of  the  surface,  which  result  when  strong  alcohol  alone 
is  used,  are  avoided.  The  jar  needs  to  be  shaken  occasionally. 


22  STUDENTS   HISTOLOGY 

The  portions  of  tissue  should  be  not  more  than  one -half  to  one 
centimeter  thick. 

Alcohol  is  the  most  generally  used  of  all  hardening  and  fixing 
fluids.  Tissues  preserved  in  it  will  keep  indefinitely,  especially  if 
the  strong  alcohol  be  replaced  by  eighty  per  cent,  alcohol  after  a 
time.  When  bacteria  are  to  be  demonstrated  in  the  organs,  alcohol 
is  as  good  as  any  agent  that  can  be  used.  But  when  the  blood, 
the  nuclear  figures,  the  elements  of  the  nervous  system,  and  the 
finer  points  in  histological  structure  are  to  be  studied,  other  fluids 
are  more  suitable. 

MULLER'S   FLUID 

Bichromate  of  potassium 2.5  grams. 

Sulphate  of  sodium 1      gram. 

Water 100      c.c. 

Miiller's  fluid  is  one  of  the  most  valuable  of  all  fixing  agents. 
The  time  required  for  hardening  is  six  weeks  or  more,  but  harden- 
ing may  be  hastened  by  placing  the  jar  in  an  incubator.  The 
pieces  of  tissue  must  be  small.  The  fluid  must  not  become  dis- 
colored, and  must  be  changed  frequently  at  first.  It  is  most 
valuable  for  nervous  tissues,  which  harden  only  after  months. 
After  hardening,  the  tissues  must  be  washed  in  running  water  for 
twenty -four  hours,  and  are  then  placed  in  alcohol,  except  nervous 
tissues,  which  are  placed  in  strong  alcohol  without  washing, 
when  the  Weigert  haematoxylin  stain  is  to  be  used.  Miiller's 
fluid  preserves  the  blood  -  corpuscles  in  the  organs  admirably. 
The  hardening  can  be  hastened  by  adding  ten  per  cent,  of 
formaldehyde  (forty  per  cent,  solution).  This  mixture  is  known 
as  ORTH'S  FLUID.  '  It  has  the  advantages  of  Miiller's  fluid,  while 
the  hardening  is  completed  in  a  week  or  less. 

FORMALDEHYDE  is  a  gas  which  is  manufactured  in  a  forty  per 
•cent,  solution  in  water.  The  solution  has  a  very  pungent  and 
irritating  odor,  and  is  a  powerful  germicide.  It  is  most  valuable 
for  preserving  large  anatomical  and  pathological  specimens,  which 
keep  their  natural  colors  in  it  much  better  than  in  alcohol.  It  is 
also  useful  in  histological  work  as  a  fixing  agent.  Pieces  of  tissue 
one  centimeter  thick  are  hardened  in  twenty -four  hours  in  ten 
parts  of  the  forty  per  cent,  formaldehyde  solution  of  commerce,  and 
ninety  parts  of  water.  Very  small  pieces  of  tissue  may  be 
hardened  in  formaldehyde  for  a  few  hours,  and  excellent  sections 


FLEMMING'S   SOLUTION  23 

may  then  be  cut  directly  after  freezing.  The  staining  properties 
of  tissues  hardened  in  this  fluid  are  well  preserved.  The  speci- 
mens may  be  kept  in  it  indefinitely. 

PICRIC    ALCOHOL     (GAGE) 

Picric  acid 2  grams. 

Alcohol 500  c.c. 

Water 500  c.c. 

This  is  an  excellent  fixing  agent  for  most  tissues.  Hardening 
is  completed  in  one  to  three  days. 

OSMIC  ACID  is  sold  in  hermetically  sealed  capsules.  It  is  used 
in  one  per  cent,  solution  in  distilled  water,  The  solution  should  be 
freshly  made  when  possible.  It  deteriorates  in  the  light,  and  must 
be  kept  in  a  dark  closet.  Its  vapor  is  very  irritating.  The  use- 
fulness of  osmic  acid  depends  largely  upon  its  property  of  staining 
fat  black.  It  is  often  employed  in  pathology.  In  histology  it  is 
most  valuable  for  nervous  tissues.  It  stains  the  medullary  sheaths 
of  medullated  nerve-fibers  black.  The  pieces  of  tissue  must  be  not 
more  than  four  millimeters  thick,  as  osmic  acid  has  very  feeble 
penetrating  power.  They  are  left  in  the  solution  twenty -four 
hours,  washed  thoroughly,  and  transferred  to  eighty  per  cent, 
alcohol.  In  preparing  specimens  for  microscopical  study,  it  is  best 
to  avoid  using  turpentine  or  xylol,  which  dissolve  the  stained  fat, 
if  that  is  to  be  preserved. 

FLEMMING'S   SOLUTION 

Two  per  cent,  osmic  acid  solution 4  parts. 

One  per  cent,  chromic  acid  solution      15  parts. 

Glacial  acetic  acid 1  part. 

The  pieces  of  tissue  should  be  four  millimeters  or  less  in  thick- 
ness. They  are  left  in  the  fluid  twenty-four  hours,  and,  after 
thorough  washing,  are  transferred  to  alcohol.  This  fluid  is 
designed  to  preserve  the  karyokinetic  figures,  using  safranin  or 
hasmatoxylin  to  stain  them.  It  is  also  admirable  to  fix  cellular 
structures  in  general,  and  it  stains  fat  black  as  well  as  osmic  acid 
alone. 

Another  formula  proposed  by  Flemming  for  fixing  the  karyo- 
kinetic figures  consists  of 

Chromic  acid 2  grams. 

Glacial  acetic  acid 1  c.c. 

Water  .  100.0  c.c. 


24  STUDENTS    HISTOLOGY 

It  serves  very  well  all  the  purposes  of  hardening  agents. 
Using  small  pieces,  leave  them  in  the  solution  twenty-four  hours. 
After  washing,  place  in  eighty  per  cent,  alcohol,  and  subsequently 
in  strong  alcohol.  Stain  with  safranin  or  haematoxylin . 

CHROMIC     ACID     FIXING    AND     HARDENING 

Chromic  acid  is  a  very  deliquescent  salt,  and  is  best  preserved 
by  making  a  strong  solution  at  once,  and  then  diluting  it  as  may 
be  needed.  A  stock  solution  may  be  made  as  follows: 

Chromic  acid  (crystals) 25  grams. 

Water 75  c.c. 

For  general  use,  dilute  three  parts  with  six  hundred  parts  of 
water,  which  gives  a  strength  of  nearly  one -sixth  of  one  per  cent. 

The  tissue,  as  soon  as  secured  and  properly  divided,  is  placed 
in  the  above,  remembering  the  rule  regarding  quantity.  Change 
in  twenty -four  hours  to  fresh  solution,  and  again  on  the  third  day. 
In  seven  days,  or  thereabout,  change  the  fluid  again.  The  tissue 
must  now  be  watched  carefully;  and  when,  on  cutting  through  a 
piece,  the  fluid  is  found  to  have  stained  the  blocks  completely, 
taking  from  two  to  three,  or  even  four  weeks,  remove  to  a  large  jar 
of  clear  water  and  wash,  preferably  with  running  water,  for  twenty- 
four  hours.  The  wrashing  having  removed  the  chromic  acid,  the 
tissue  is  further  hardened  in  alcohol. 

Very  small  pieces  of  tissue  maybe  hardened  in  one  or  two  days. 
Chromic  acid  is  useful  to  preserve  the  nuclear  figures. 

ERLICKl'S     FLUID 

Bichromate  of  potassium 25  grams. 

Sulphate  of  copper 10       " 

Water 1,000  c.c. 

This  may  be  employed  in  precisely  the  same  manner  as  the 
dilute  chromic  acid  solution. 

DECALCIFYING     PROCESS 

Six  per  cent,  chromic  acid  solution 9  parts. 

Nitric  acid,  C.  P 1  part. 

Water 90  parts. 

The  earthy  salts  may  be  removed  from  teeth  and  small  pieces  of 


IMBEDDING  25 

bone  with  a  liberal  supply  of  the  above  in  about  twenty  days.  A 
frequent  change  of  the  solution  will  greatly  facilitate  the  process, 
and  an  occasional  addition  of  a  few  drops  of  the  nitric  acid  may  be 
made  with  very  dense  bone.  After  the 'removal  of  the  lime  salts, 
the  pieces  may  be  preserved  in  alcohol  until  such  time  as  sectioi 
are  needed,  when  they  may  be  cut  with  the  microtome  without 
injury  to  the  knife. 

DISSOCIATING    PROCESS    (w.    STIRLING) 

Artificial    Gastric  Fluid 

Pepsin 1  gram. 

Hydrochloric  acid      1  c.c. 

Water 500  c.c. 

This  process  depends  for  its  value  upon  the  fact  that  certain 
connective  tissues  are  more  rapidly  dissolved  by  the  fluid  than 
others. 

IMBEDDING 

The  best  and  thinnest  sections  can  only  be  cut  when  properly 
hardened  tissues  are  used,  and  when  the  meshes  of  the  tissue  have 
been  filled  with  some  substance  which  supports  the  delicate  elements. 
The  substances  used  for  this  purpose  are  paraffin  and  celloidin,  or 
collodion. 

THE     PARAFFIN    METHOD 

a.  Pieces  of  tissue  2-3  mm.  thick  are  to  be  placed  in  ninety- 
five  per  cent,  alcohol  for  twenty -four  hours. 
1).  In  pure  chloroform  six  to  eight  hours. 

c.  In  a  saturated  solution  of   paraffin  in  choloroform  two  to 
three  hours. 

d.  In  melted  paraffin,  having  a  melting  point  of  50°  C.,  which 
requires  the  use  of  a  water  bath  or  oven,  one  to  six  hours.     The 
chloroform  must  be  entirely  driven  off,  and  the  tissue  thoroughly 
infiltrated. 

e.  Change  to  fresh  paraffin  for  a  few  minutes. 

/.  Finally  jplace  the  tissue  in  a  small  paper  box  and  pour  the 
melted  paraffin  about  it.  Harden  as  quickly  as  possible  with  run- 
ning water.  It  is  important  to  fix  the  piece  of  tissue  in  a  suitable 
position,  if  the  position  is  of  importance,  before  pouring  in  the 
melted  paraffin. 


26  STUDENTS  HISTOLOGY 

Sections  of  exquisite  thinness  may  now  be  cut.  The  knife  need 
not  be  wet.  Paraffin  imbedding  is  especially  adapted  to  making 
serial  sections. 

In  order  to  mount  the  sections,  proceed  as  follows: 

a.  Place  the  sections  on  a  slide.     Add  a  thin  solution  of  gum 
arabic,  upon  which  they  float.     Warm  slightly,  when  the  sections 
will  flatten  nicely.     Drain  off  the  superfluous  gum  solution,  leaving 
the  sections  in  their  proper  positions.      Let  them   dry  for  some 
hours,  and  they  will  be  firmly  fastened  to  the  slide. 

b.  Dissolve  out  the  paraffin  in  one  of  the  numerous  solvents 
(xylol,  half  an  hour  or  less). 

c.  At  this  point,  unless  the  piece  of  tissue  was  stained  in  bulk 
before  imbedding,  the  xylol  should  be  washed  off  with  alcohol  and 

d.  The   section  stained  with  one  of   the    dyes  described   here- 
after. 

e.  Dehydrate  in  alcohol. 

/.  Clear  in  some  suitable  agent,  as  xylol  or  oil  of  cloves. 
g.  Mount  in  balsam. 


CELLOIDIN     INFILTRATION 

Certain  structures  require  permanent  support — i.e.,  not  only 
while  being  cut,  but  during  the  subsequent  handling  of  the  sec- 
tions. The  celloidin  infiltrating  process  is  best  adapted  to  such 
material.  Considerable  time  is  needed  for  the  successful  employ- 
ment of  the  process,  but  results  can  be  secured  that  cannot  be 
equaled  with  any  other  method. 

Celloidin  is  the  proprietary  name  of  a  sort  of  pyroxylin,  very 
soluble  in  a  mixture  of  ether  and  alcohol,  producing  a  collodion. 
If  thick  collodion  be  exposed  for  a  few  moments  to  the  air  it 
becomes  semi -solid — not  unlike  boiled  egg -albumen;  and  to  this 
property  is  due  the  value  of  a  solution  of  celloidin  in  histology.  It 
may  be  used  as  follows: 

To  a  mixture  of  equal  parts  of  ether  and  alcohol  add  celloidin* 
until  the  thickest  possible  solution  has  been  obtained. 

A  piece  of  alcohol -hardened  tissue,  having  been  selected  and 
kept  for  the  preceding  twenty -four  hours  in  a  mixture  of  equal 
parts  of  alcohol  and  ether,  is  placed  in  about  an  ounce  of  the  solu- 


*We  find,  after  repeated  trial,  that  the  ordinary  soluble  gun-cotton,  such  as  is  employed  by 
photographers,  is  in  no  way  inferior  to  the  celloidin. 


STAINING    AGENTS   AND    METHODS  27 

tion  and  allowed  to  remain  twenty -four  hours.     The  bottle  con- 
taining the  whole  should  be  well  corked,  to  prevent  evaporation. 

The  tissue  after  infiltration  is  to  be  placed  on  a  wooden  block, 
and  allowed  to  remain  in  the  open  air  for  a  few  minutes,  after 
which  it  should  be  plunged  into  a  mixture  of  alcohol  two  parts7 
water  one  part.  Here  it  may  remain  for  twenty -four  hours,  or 
until  wanted. 

Cut  in  the  usual  way,  using  a  mixture  of  alcohol  two  parts, 
water  one  part,  for  flooding  the  knife.  The  section  should  be 
finally  preserved  in  the  same  instead  of  pure  alcohol,  which  would 
dissolve  the  celloidin. 

In  infiltrating  the  tissue  with  the  collodion  it  is  best,  especially 
if  it  be  very  dense  in  parts,  to  use  first  a  thin  and  subsequently 
the  thick  solution.  A  more  perfect  infiltration  is  often  obtained 
in  this  way.  In  some  cases  we  have  been  obliged  to  continue  the 
maceration  for  several  days.  The  solution  should  be  kept  in  well 
stoppered  bottles,  as  the  ether  is  exceedingly  volatile.  Should  the 
collodion  at  any  time  become  solid  from  evaporation,  it  may  be 
easily  dissolved  by  adding  the  ether  and  alcohol  mixture. 

The  process  is  of  inestimable  value  where  delicate  parts  are 
weakly  supported,  and  where  it  is  important  to  preserve  the  normal 
relations.  The  gelatin -like  collodion  permeates  every  space,  and 
as  it  is  not  to  be  removed  in  the  future  handling  of  the  sections, 
it  affords  a  support  to  portions  that  would  otherwise  be  lost  or 
distorted.  It  offers  no  obstruction  to  the  light,  being  perfectly 
translucent  and  nearly  colorless. 


STAINING    AGENTS   AND    METHODS 
STAINING    FLUIDS 

It  is  a  very  interesting  fact  (and  one  upon  which  our  present 
knowledge  of  histology  largely  depends)  that,  on  examination  of 
tissues  which  have  been  dyed  with  special  colored  fluids,  the  dye 
will  be  found  to  have  colored  certain  anatomical  elements  very 
deeply,  others  slightly,  while  others  still  remain  unstained. 

Certain  dyes  are  called  general  or  ground  stains,  because 
they  stain  all  parts  of  a  tissue  alike,  or  nearly  so.  Others,  which 
are  entitled  selective,  exhibit  an  affinity  for  some  particular  struc- 
ture, usually  the  nucleus  of  the  cell.  Haematoxylin,  or  logwood, 
for  instance,  has  such  an  affinity  for  nuclei.  The  whole  nucleus  is 


28  STUDENTS    HISTOLOGY 

not  stained,  but  certain  threads  in  it,  which  ordinarily  appear  as 
granules.  This  part  of  the  nucleus  is  called  chromatin,  on  account 
of  its  affinity  for  dyes.  In  a  tissue  colored  with  haBmatoxylin,  the 
minute  granules  of  the  nuclei  are  so  deeply  stained  in  the  logwood 
dye  as  to  appear  almost  black.  The  nuclei  are  plainly  stained,  while 
the  limiting  membrane  of  cells  is  usually  but  slightly  colored.  Old, 
dense  connective  tissues  stain  feebly,  or  fail  entirely  to  take  color. 
The  differentiation  is,  without  doubt,  due  to  chemical  action 
between  the  elements  of  the  dye  and  those  of  the  tissue. 

A  very  great  number  and  variety  of  materials  have  been  used 
for  histological  differentiation,  and  a  simple  enumeration  of  them 
all  would  very  nearly  fill  the  remainder  of  our  pages.  It  will  be 
found,  however,  that  leading  histologists  confine  themselves  to  two 
or  three  standard  formulas  for  general  work.  We  shall  notice  only 
those  methods  that  have  been  thoroughly  demonstrated  by  years 
of  employment  as  best  for  the  purpose  suggested.  Special  cases 
will  require  special  treatment,  which  will  be  indicated  in  proper 
connection. 

It  is  important  in  all  cases  to  secure  the  purest  and  most  con- 
centrated dyes  obtainable.  It  is  better  to  make  your  own  solutions 
than  to  buy  them  already  prepared. 

DELAFIELD '  S     H^M  ATOXYLIN 

Haematoxylin  crystals 4  grams. 

Alcohol 25  c.c. 

Ammonia  alum  . 50  grams. 

Water 400  c.c. 

Glycerin 100  c.c. 

Methyl  alcohol 100  c.c. 

Dissolve  the  haematoxylin  in  the  alcohol,  and  the  ammonia  alum 
in  the  water.  Mix  the  two  solutions.  Let  the  mixture  stand  four 
or  five  days  uncovered ;  it  should  have  become  a  deep  purple. 
Filter  and  add  the  glycerin  and  the  methyl  alcohol.  After  it  has 
become  dark  enough  filter  again.  Keep  it  a  month  or  longer  * 
before  using  ;  the  solution  improves  with  age.  At  the  time  of 
using,  filter  and  dilute  with  water  as, desired. 

EOSIN 

Eosin  is  an  aniline  dye,  sold  in  the  form  of  a  red  powder.  It  is 
best  to  keep  on  hand  a  saturated  solution  in  alcohol.  A  few  drops 


STAINING   FLUIDS  29 

i 

of  this  stock  solution  may  be  added  to  a  small  dish  full  of  water  at 
the  time  of  using. 

BORAX  -  CARMINE  (GRENACHER) 

Carmine 2.5  grams. 

Borax 4.0  grams. 

Alcohol  (70%) 100.0  c.e. 

Water 100.0  c.c. 

Rub  the  carmine  and  borax  together.  Dissolve  them  in  the 
water,  which  should  be  hot.  The  alcohol  may  be  added  when  the 
mixture  is  cold.  The  stain  will  be  available  after  two  weeks,  but 
improves  with  age.  This  solution  is  especially  suitable  for  the 
staining  of  whole  masses  of  tissue  before  imbedding,  i.e.,  in  bulk. 
For  staining  in  bulk,  leave  the  tissue  in  the  carmine  for  twenty- 
four  hours.  It  may  be  used  for  sections,  however,  which  are  to  be 
left  in  the  stain  fifteen  minutes  or  longer.  In  all  cases  carmine 
staining  is  to  be  finished  with  the  use  of  acid  alcohol,  which  diifer- 
entiates  the  elements. 

ACID    ALCOHOL 

Alcohol  (70%} 100  c.c. 

Hydrochloric  acid  (strong) 1  c.c. 

Sections  stained  in  carmine  are  placed  in  acid  alcohol  for  a  few 
minutes.  They  acquire  a  brilliant  scarlet  color.  For  specimens 
stained  in  bulk,  dilute  the  acid  alcohol  with  twice  as  much  70  per 
cent,  alcohol,  and  leave  the  tissue  in  the  mixture  twenty-four  hours. 

PICRO- CARMINE 

Carmine 1  gram. 

Aqua  ammonia  (strong) 5  c.c. 

Water 50  c.c. 

Saturated  watery  solution  of  picric  acid    .    .    .    .  50  c.c. 

Add  the  picric  acid  solution  after  dissolving  the  carmine  in  the 
diluted  ammonia.  Let  the  mixture  stand  uncorked  for  two  days, 
and  filter.  The  carmine  gives  a  nuclear  stain,  while  the  picric  acid 
serves  as  a  counter  stain. 

IODINE    SOLUTION 

Iodine 1  gram. 

Potassium  iodide 2  grams. 

Water    .  .  300  c.c. 


30  STUDENTS  HISTOLOGY 

i 

WEIGERT-PAL     H^MATOXYLIN     METHOD 

This  stain  is  employed  for  nervous  tissues  containing  medullated 
nerve -fibers.  The  medullary  sheaths  of  these  fibers  are  stained 
intensely  black,  while  the  other  elements  of  the  tissue  remain  pale. 
It  is  used  chiefly  for  the  spinal  cord  and  the  brain. 

The  tissue  is  first  hardened  in  Miiller's  fluid.  Unless  the  pieces 
of  tissue  are  very  small,  the  hardening  requires  months.  The 
fluid  must  be  changed  frequently.  Hardening  is  completed  in 
strong  alcohol,  without  washing  in  water.  Imbed  in  celloidin. 

The  sections  are  overstained  with  haBmatoxylin,  and  subse- 
quently are  partly  decolorized.  The  medullary  sheaths  retain  the 
stain  with  greater  tenacity  than  the  other  elements  of  the  tissue. 
The  solutions  used  are  as  follows: 

Hsematoxylin  crystals 1  gram. 

Alcohol 10  c.c. 

Water 90  c.c. 

Boil  and  filter.  Allow  the  solution  to  stand  a  week  or  two.  If 
used  sooner,  add  a  drop  of  saturated  solution  of  lithium  carbonate 
to  a  part  of  the  stain  in  a  small  dish. 

Permanganate  of  potassium 1  gram. 

Water 400  c.c. 

One  per  cent,  solution  of  oxalic  acid. 

One  per  cent,  solution  of  sodium  or  potassium  sulphite. 

Mix  the  oxalic  acid  and  sodium  sulphite  in  equal  parts  at  the 
time  of  using.  Sulphurous  acid  is  formed. 

The  steps  in  staining  are  as  follows: 

a.  Sections  are  placed  in  the  haematoxylin  for  twenty -four 
hours,  and  are  intensely  stained,  becoming  nearly  black.  The  pro- 
cess may  be  hastened  by  letting  them  stand  in  an  incubator,  where 
they  may  be  sufficiently  stairned  in  a  few  hours. 

6.  Wash  in  water. 

c.  Place  the  sections  in  the  permanganate  of  potassium  until 
they  acquire  a  dark  brown  color  (one -half  to  five  minutes). 

d.  Wash  in  water. 

e.  Place  the  sections  in  the  mixture  of  oxalic  acid  and  sodium 
sulphite.     The  brown  color  should  give  way  to  a  blue  black  in  the 
white  matter,  while  the  gray  matter  becomes  nearly  white.     If  the 
sections  remain  too  dark  they  may  be  returned  to  the  permanganate 


ANILINE   DYES  31 

for  a  few  minutes,  and  then  to  the  sulphurous  acid  again,  always 
washing  in  water  between  the  two  changes. 

/.  Wash  thoroughly  in  water,  and  mount  in  the  usual  way  in 
balsam. 

ANILINE     DYES 

The  substances  known  as  aniline  dyes  are  derivatives  of  coal  tar, 
but  not  always  of  aniline.  These  dyes  have  become  of  great 
importance  in  all  kinds  of  biological  work.  The  number  of 
different  compounds  is  very  large,  and  only  a  few  of  the  most 
common  can  be  mentioned.  None  but  the  purest  dyes  should  be 
used,  and  those  manufactured  by  Grubler  can  be  recommended. 
They  are  sold  in  the  form  of  powders.  American  agents  for 
Grubler 's  dyes  are  Eimer  &  Amend,  of  New  York  city.  It  is 
simplest  to  classify  the  dyes  as  basic  or  acid.  Fuchsin,  methylene 
blue,  gentian  violet,  and  safranin  are  basic  dyes.  They  have  an 
affinity  for  nuclei  and  for  bacteria.  Eosin,  picric  acid,  and  acid 
fuchsin  are  acid  dyes,  tending  to  stain  tissues  diffusely.  The  use  of 
eosin  and  picric  acid  has  been  described  on  pages  28  and  29. 

Certain  cells  have  granules  in  their  protoplasm.  The  granules 
of  some  cells  manifest  an  affinity  for  basic  dyes  (basophile,  S  and  y) , 
others  for  acid  dyes  (acidophile  or  eosinophile,  «),  and  others 
for  a  mixture  of  the  two  (neutrophile,  *),  and  others  still  for  both 
the  acid  and  the  basic  (amphophile,  ft). 

It  is  best  to  keep  on  hand  saturated  alcoholic  solutions  of  these 
dyes,  from  which  waterjr  solutions  may  be  made  when  needed, 
by  adding  a  few  drops  of  the  alcoholic  solution  to  a  small  dish 
filled  with  water. 

The  basic  dyes  may  be  used  as  nuclear  stains  as  follows : 

a.  Stain  sections  in  a  strong  watery  solution  of  the  dye  five 
minutes  or  more.  The  sections  will  be  somewhat  overstained. 

5.  Wash  in  one  per  cent,  acetic  acid  a  few  seconds. 

c.  Alcohol.      Dehydration   must   be   done   rapidly,   as   alcohol 
extracts   the   color   from   the   tissues.     It   must,  nevertheless,  be 
thorough,  as  xylol,  which  is  used  in  the  next  step,  only  mixes  with 
strong  alcohol. 

d.  Xylol.     This  agent  is  the  one  used  to  clear  specimens  after 
staining  with  basic  aniline  dyes,  because  most  of  the  oils  slowly 
dissolve  out  the  aniline  colors. 

e.  Balsam. 

Among  the  dyes  used  in  this  manner,  SAFRANIN  is  to  be  espe- 


32  STUDENTS  HISTOLOGY 

cially  recommended  as  a  nuclear  staiii.  The  sections  are  treated 
according  to  the  programme  just  given,  except  that  they  should 
remain  in  the  safranin  solution  (one  per  cent.)  some  hours. 
Safranin  has  been  employed  largely  in  staining  karyokinetic 
figures,  after  hardening  with  Flemming's  solution  (page  23). 

NIGROSIN  is  an  aniline  color  used  mostly  for  nervous  tissues. 
It  is  valuable  when  results  are  desired  at  once,  without  waiting 
for  the  tedious  hardening  process  required  for  the  Weigert-Pal 
method. 

a.  Stain  sections  in  strong  watery  solution  of  nigrosin  five  to 
ten  minutes. 

&.  Wash  and  mount  in  the  usual  way  in  balsam,  clearing  in 
xylol. 

VAN   GIBSON'S   STAIN 

Acid  fuchsin  (one  per  cent,  watery  solution)  .    .    .  15  c.c. 

Picric  acid  (saturated  watery  solution) 50  c.c. 

Water 50  c.c. 

a.  Stain  sections  in  haematoxylin. 
&.  Wash  in  water. 

c.  Stain  in  the  picric  acid  and  acid  fuchsin  from  three  to  five 
minutes. 

d.  Wash  in  water  and  mount  in  the  usual  way  in  balsam. 

The  Van  Gieson  stain  is  used  chiefly  for  connective  and  nervous 
tissues. 

EHRLICH     TRICOLOR     STAIN 


Saturated  watery  solution  orange  G.    .    .    . 
"                                        acid  fuchsin    .    . 
"               "             ll         methyl  green    . 
Glycerin  • 

.  120-135  c.c. 
.    80-165  c.c. 
125  c.c. 
100  c  c 

Absolute  alcohol  
Distilled  water  . 

,    .          200  c.c. 
300  c.c. 

This  formula  is  only  one  of  a  number  with  which  Ehrlich's 
name  is  associated,  as  well  as  those  of  Biondi  and  Heidenhain.  A 
powder  containing  the  dyes  already  mixed  is  sold  by  dealers,  and 
usually  works  very  well.  It  may  be  used  to  stain  sections  of 
tissues,  but  is  employed  mostly  with  preparations  of  blood,  dried 
on  cover -glasses  and  fixed  lay  heating.  Stain  five  minutes  or  less. 
It  is  designed  to  stain  the  neutrophile  granules  of  certain  leucocytes, 


METALLIC    STAINS— GOLGI   METHODS  33 

which  become  colored  reddish  brown.  Eosinophile  granules 
become  brilliant  red.  Nuclei  are  stained  green  by  it,  while  the  red 
corpuscles  are  orange -red  or  brown.  Its  use  will  be  referred  to  in 
the  chapter  on  blood. 

METALLIC     STAINS     OR    IMPREGNATIONS 

Compounds  of  silver,  gold,  mercury,  and  osmium  are  used  to 
color  particular  elements  in  the  tissue,  or  they  are  precipitated  in 
certain  structures  as  opaque  deposits.  Osmic  acid  has  already  been 
described  on  page  23.  Of  the  other  substances,  NITRATE  OP  SILVER 
is  the  most  important. 

This  salt  is  used  in  dilute  solutions  (1-300,  1-500)  made 
with  distilled  water.  It  is  most  valuable  to  stain  the  cement-sub- 
stance between  the  endothelial  cells  of  membranes,  like  the  peri- 
toneum. The  membrane  is  stained  while  fresh,  and  must  be 
washed  free  of  all  albuminous  substances  which  might  precipitate 
the  silver.  It  should  also  be  stretched  over  the  rim  of  a  dish. 
The  solution  of  nitrate  of  silver  should  be  allowed  to  act  upon  the 
membrane,  care  being  taken  to  have  it  reach  all  parts  of  the 
surface.  It  has  little  penetrating  power.  After  five  to  ten  minutes 
wash  in  water,  and  expose  to  the  sunlight,  in  which  the  color 
becomes  brown,  owing  to  dark  lines  which  develop  between  the 
cells.  Mount  in  glycerin  or  balsam. 

GOLGI    METHOD    FOR     STAINING     BRAIN    AND     SPINAL     CORD 

There  are   many  formulas  which   different  investigators  have 
used  with  more  or  less  success.     All  of  them  seek  to  impregnate 
the  tissue  with  silver  or  mercury  salts,  which  become  precipitated 
on  £ome  of  the  nerve-elements  and  render  them  visible.     At  best, 
the  Golgi  method  is  uncertain,  but  when  it  is  successful,  the  prep- 
arations obtained  are  of  great  beauty  and  value. 
The  following  procedure  can  be  recommended  : 
a.  Small  pieces  of   fresh  tissue  are    hardened  from  two   days 
to  a  week  in 


Osmic  acid,  one  per  cent 10  c.c. 

Potassium  bichromate,  three  and  one -half  per  cent.  40  c.c. 


The  time  required  varies  according  to  the  part  of   the  tissue 
to  be  stained.     Neuroglia  requires  the  shortest  and  nerve-fibers  the 

c 


34  STUDENTS   HISTOLOGY. 

longest  time.     For  ganglion-cells  the  time  should  be  intermediate 
between  these. 

b.  The   tissue  is  placed  in  a  three -fourths  per  cent,  solution  of 
nitrate  of  silver  for  one  to  six  days. 

c.  Cut  rather  thick  sections,  about  50  p.     Alcohol  is  to  be  used 
as  little  as  possible.     Sections  may  be  cut  free-hand  or  between 
pieces  of  elder -pith,  or  by  fastening  on  the  block  with  paraffin 
(page    18);   or   by  imbedding   rapidly  in    celloidin,  taking   about 
twenty  minutes  for  all  the  steps. 

d.  Alcohol,  xylol,  and  balsam,  as  usual. 

e.  Mount  without  a  cover -glass,  and  keep  in  the  dark. 

COX'S    MODIFICATION    OF    THE    GOLGI    METHOD 

Golgi  found  that  the  bichloride  of  mercury  could  be  used  for 
the  impregnation  of  nervous  tissues  in  much  the  same  manner  as 
the  nitrate  of  silver.  The  formula  proposed  by  Cox  has  been 
highly  recomended. 

Bichromate  of  potassium  (five  per.  cent. solution)  20  parts. 
Bichloride  of  mercury  (five  per  cent,  solution)  .  .  20  parts. 
Simple  chromate  of  potassium  (five  per  cent,  sol.)  16  parts. 
Distilled  water 30  to  40  parts. 

Specimens  should  be  left  in  the  mixture  for  one  month  in  sum- 
mer, and  for  two  to  three  months  in  winter.  The  impregnation 
should  take  place  uniformly  throughout  the  preparation. 

INJECTION     OF    BLOOD-VESSELS 

To  make  the  small  blood-vessels  appear  in  microscopical  prep- 
arations they  may  be  filled  with  some  colored  substance.  An 
entire  animal  recently  killed,  or  merely  one  organ,  may  be  injected. 
A  canula  is  tied  in  the  proper  vessel  and  injected  with  a  syringe,  or 
from  a  flask  holding  the  coloring  substance,  which  is  emptied  by 
mercurial  or  water  pressure.  Among  many  formulas  for  injecting 
fluids,  the  following  may  be  used: 

Soluble  Berlin  blue  .    . 3  grams. 

Water 600  c.c. 

This  mixture  has  the  advantage  that  it  may  be  used  cold. 
CARMINE-GELATIN  must  be  kept  warm  while  injection  is  pro- 
ceeding, as  must  the  object  which  is  being  injected.     Two  and  one- 


CLEARING    AGENTS— MOUNTING    MEDIA  35 

half  grams  of  carmine  are  rubbed  up  with  a  little  water,  and  strong 
ammonia  added,  a  drop  at  a  time,  till  the  carmine  is  dissolved. 
Then  filter.  Five  grams  of  gelatin  having  previously  been  dis- 
solved in  water,  add  the  carmine  solution.  Now  neutralize  the 
carmine -gelatin  exactly  with  acetic  acid.  As  the  neutral  point  is 
approached,  the  acid  must  be  diluted  and  added  cautiously; 
filter. 

CLEARING    AGENTS 

The  commonest  method  of  preparing  sections  is  to  mount  them 
finally  in  Canada  balsam.  Staining  is  usually  performed  in  watery 
solutions.  Water  does  not  mix  with  balsam.  After  staining, 
therefore,  the  water  is  to  be  removed  with  alcohol,  which  has  an 
affinity  for  water.  The  alcohol  must  in  turn  be  removed  with  some 
substance  which  will  mix  with  balsam.  The  various  fluids  used 
for  clearing  have  this  property,  and  also  make  the  tissue  trans- 
parent. ANILINE  OIL  is  a  clearing  agent  which  will  itself  remove 
water  from  the  tissues  without  the  use  of  alcohol.  It  does  not  dis- 
solve celloidin.  It  extracts  the  aniline  colors,  however.  XYLOL  can 
only  be  used  when  dehydration  is  perfect.  It  does  not  dissolve 
celloidin,  nor  extract  the  aniline  dyes.  It  is  often  used  mixed  with 
one -third  of  its  volume  of  carbolic  acid — CARBOL-XYLOL.  When  an 
agent  that  will  not  dissolve  celloidin  is  desired,  a  cheap  and  excel- 
lent substitute  for  the  last  is  the  CARBOL- TURPENTINE  of  Gage: 

Carbolic  acid  crystals  (melted) 40  c.c. 

Oil  of  turpentine CO  c.c. 

The  essential  oils  and  CREOSOTE  are  used  frequently  for  clear- 
ing, for  example,  the  OILS  of  ORIGANUM,  of  BERGAMOT,  and  of 
THYME.  OIL  OP  CLOVES  is  used  very  extensively,  but  it  has  the 
property  of  removing  the  aniline  dyes  quite  rapidly,  and  it  dissolves 
celloidin.  It  may  be  used  to  clear  celloidin  sections,  except  the 
most  delicate,  if  care  be  used.  Delicate  sections  should  be  cleared 
on  the  slide.  Other  sections  may  be  placed  in  a  small  dish  of  the 
clearing  fluid. 

MOUNTING    MEDIA 

CANADA  BALSAM  is  the  medium  most  used  for  the  permanent 
preservation  of  microscopical  preparations.  It  should  be  dissolved 
in  xylol,  which  does  not  affect  the  aniline  stains. 


36 


STUDENTS   HISTOLOGY 


DAMMAR  is  sometimes  used  in  the  same  manner  as  balsam. 
Balsam  and  dammar  may  be  kept  in  large-mouthed  bottles,  from 
which  they  are  removed  with  glass  rods.  They  are  also  sold  in 
flexible  lead  tubes,  which  make  a  convenient  way  of  handling 
them. 

Fresh  tissues  are  often  studied  in  a  six -tenths  Of  one  per 
cent,  solution  of  sodium  chloride  in  water — NORMAL  SALT  SOLUTION. 


FIG.  15.     USING  TURN-TABLE— AFTER  FREEBORN. 

Objects  are  often  mounted  in  GLYCERIN,  especially  those  that 
would  be  injured  by  alcohol.  It  is  best  to  use  a  circular  cover- 
glass,  and  to  surround  the  edge  with  some  soluble  cement,  using  a 
turn-table  for  this  purpose. 

Zinc  cement,  asphalt  varnish,  and  other  suitable  cements  may 
be  purchased  from  dealers  in  microscopical  supplies. 


STAINING    METHODS 
H^MATOXYLIN     STAINING     PROCESS 

You  will  require  for  future  work  a  needle  like  Fig.  16,  several 
saucers,  preferably  of  white  ware;  a  few  watch-glasses  (large,  odd 
sizes  are  usually  cheaply  obtainable  at  a  jeweler's) ;  half  a  dozen 


FIG.  16.     NEEDLE  FOR  LIFTING  SECTIONS,  ETC. 

glass  saltcellars— small  ones  known  as  "individual  salts," — and 
a  two -ounce,  shallow,  covered  porcelain  box,  such  as  druggists 
use  for  ointments,  dentifrices,  etc. 

Place  on  the  work-table  (best  located  so  as  to  be  lighted  from 
your  side  and  not  from  the  front)  in  order,  as  in  Fig.  17: 


H&MATOXYLIN   STAINING    PROCESS 


37 


1.  Watch-glass,  containing  say  10  c.c.  diluted  haematoxylin. 

2.  Saucer,  filled  with  water. 

3.  Saltcellar,  filled  with  alcohol. 

4.  The  covered  porcelain  box,   containing   about   20  c.c.  oil   of 
cloves*  or  carbol- turpentine. 

Select  a  section  from  some  one  of  your  stock  bottles,  lifting  it 
out  with  the  needle,  and  place  it  in  the  haematoxylin  solution.    The 


FIG.  17. 


DIAGRAM  INDICATING  THE  SUCCESSIVE  STEPS  IN  STAINING  WITH 
THE  HAEMATOXYLIN  SOLUTION. 


section,  having  been  taken  from  alcohol  and  transferred  to  a 
watery  staining  fluid,  will  twirl  about  on  the  surface  of  the  latter, 
inasmuch  as  currents  are  formed  by  the  union  of  the  water  and  the 
spirit. 

"How  long  shall  I  let  the  section  remain  in  the  haematoxylin ? " 
The  only  answer  we  can  give  is,  "Until  properly  stained."  Nothing 
but  experience  will  give  you  any  more  definite  information.  Much 
depends  upon  some  peculiar  property  in  the  tissues:  some  stain 
rapidly,  others  stain  very  slowly.  The  strength  of  the  dye  is 
another  determining  factor.  Usually  with  the  haematoxylin  form- 
ula, as  given,  from  two  to  three  minutes  will  suffice. 

Place  the  needle  under  the  section  (if  the  fluid  be  so  opaque  as 
to  hide  the  tissue,  place  the  watch-glass  over  a  piece  of  white  paper 
or  a  bit  of  mirror)  and  gently  lift  it  out;  drain  off  the  adhering 
drop  of  dye  on  the  edge  of  the  glass,  and  drop  into  the  saucer  of 
water.  Here  we  can  judge  as  to  the  color,  and  we,  perhaps,  find  it 
to  be  of  a  light  purple — too  light,  so  you  may  return  it  to  the 
haematoxylin  for  another  period  of  two  or  three  minutes,  which 
will  probably  give  sufficient  depth. 

As  the  section  floats  on  the  washing  water,  you  will  notice  that 
the  latter  will  be  colored  by  the  dye,  some  of  which  leaves  the 

*Although  oil  of  cloves  is  the  clearing  agent  mentioned  throughout  this  book,  it  is  to  be 
remembered  that  it  dissolves  celloidin,  and  that  carbol -turpentine  is  preferable  for  sections  if 
they  are  delicate. 


38  STUDENTS   HISTOLOGY 

tissue.  Allow  the  water  to  act  until  no  more  color  comes  out. 
The  tint  of  the  section  changes  from  purple  to  violet,  and  the  water 
must  be  allowed  to  act  until  the  change  is  complete. 

If  you  were  to  examine  your  section  at  this  stage,  you  would 
find  it  opaque,  and  as  we  are  obliged  to  study  our  objects  mainly 
by  transmitted  light,  we  must  find  some  means  of  securing  trans- 
lucency.  The  essential  oils  are  used  for  this  purpose,  oil  of  cloves 
being  commonly  employed.  Lift  the  section  from  the  water  with 
the  needle,  let  it  drain  a  moment,  and  then  drop  it  into  the  alcohol 
with  which  the  saltcellar  was  filled.  The  object  of  this  bath  is  the 
removal  of  the  water  from  the  tissue,  and  this  will  be  accomplished 
in  from  five  to  ten  minutes.  Again  lift  the  section  and  place  it  in 
the  oil  of  cloves.  The  tissue  floats  out  flat,  and  in  a  few  minutes 
sinks  in  the  oil. 

We  might  proceed  to  the  examination  of  the  stained  section; 
but  we  shall  ask  you  to  let  it  remain  in  the  oil,  covering  the  box 
carefully  to  exclude  our  great  enemy,  dust,  until  we  have  learned 
more  about  staining. 

To  recapitulate:  The  essential  steps  in  the  haematoxylin  pro- 
cess are: 

1.  Staining  the  tissue — haematoxylin. 

2.  Washing — water. 

3.  Dehydrating — alcohol. 

4.  Rendering  transparent — oil  of  cloves. 

As  the  section  is  put  in  the  dye,  care  should  be  taken  to  so  float 
it  out  that  it  may  not  be  curled.  This  is  easily  done  with  the 
needle.  After  the  alcohol  bath,  however,  this  becomes  difficult,  as 
the  tissue  is  rendered  stiff  by  the  removal  of  the  water. 

This  is  the  simplest  and  best  of  all  methods  for  general  work, 
and  you  are  advised  to  master  every  detail  of  the  process.  After 
reading  the  directions  which  we  have  given,  and  having  never  seen 
the  work  actually  done,  it  will  not  be  singular  if  you  conclude 
that  the  staining  of  tissues  is  a  tedious  and  slow  process;  but  after 
a  month's  work  you  will  be  able  to  stain  fifty  different  sections  in 
half  an  hour,  and  have  them  ready  for  mounting. 

HJEMATOXYLIN    AND     EOSIN— DOUBLE     STAINING 

Very  beautiful  and  valuable  results  in  differentiation  are 
obtained  by  staining  first  with  haematoxylin  and  subsequently  with 
eosin.  Eosin,  a  coal-tar  derivative,  stains  most  animal  tissues 


BORAX- CARMINE    STAINING   PROCESS 


39 


pink,  and  it  affords  with  the  ha3matoxylin  a  good  contrasting  color. 
The  tissue  is  to  be  stained  in  haBmatoxylin  and  washed  in  water  as 
usual ;  then  it  is  placed  in  the  eosin  solution,  and  afterward 
washed  again.  The  subsequent  treatment  is  as  with  the  plain 
hromatoxyliii  process;  viz.,  dehydration  with  alcohol,  after  whicji 
the  oil  of  cloves. 

The  diagram,  Fig.  18,  shows  the  process  complete: 

1.  Watch-glass  with  ha3matoxylin. 

2.  Saucer  with  water. 

3.  Watch-glass  two -thirds  filled  with  water,  with  five  drops  of 
eosin  solution  added. 

4.  Saucer  containing  water. 

5.  Saltcellar  filled  with  alcohol. 

6.  Covered  oil -dish. 

The   eosin   stains  very  quickly,  generally  in  about  a  minute. 
Care  should  be  taken  not  to  overstain  with  it,  as  it  cannot  be 


FIG.   18. 


DIAGRAM  INDICATING  THE  SUCCESSIVE  STEPS  IN  DOUBLE  STAINING  WITH 
H^EMATOXYI.IN  AND  EOSIN. 


washed  out.  If  the  sections  are  found  at  any  time  to  be  over- 
stained  with  haematoxylin  the  color  may  be  removed  to  any  desired 
extent  by  floating  them  in  a  weak  solution  of  acetic  acid.  They 
must  afterward  be  washed  very  thoroughly  in  clean  water. 

BORAX -CARMINE     STAINING     PROCESS 

Arrange  your  materials  as  in  the  diagram,  Fig.  19. 

1.  Watch-glass  two -thirds  filled  with  the  carmine  fluid. 

2.  Saucer  containing  about  an  ounce  of  alcohol. 

3.  Saltcellar   filled   with    alcohol    containing  one  per  cent,  of 
hydrochloric  acid. 

4.  Saltcellar  with  alcohol. 

5.  Porcelain  dish  containing  oil  of  cloves. 

The  carmine  solution  will  stain  ordinarily  in  fifteen  or  twenty 
minutes.     After  the  section  has  been  in  the  dye  for  a  few  minutes, 


40 


STUDENTS   HISTOLOGY 


lift  it  with  the  needle,  drain,  and  transfer  to  the  saucer  containing 
alcohol.  You  will  then  be  enabled  to  determine  whether  the  section 
is  sufficiently  stained;  it  should  be  a  deep,  opaque  red.  The  alcohol 
washes  off  the  section,  removing  the  adhering  solution  of  carmine. 
The  carmine  must  now  be  fixed  in  the  tissue,  or  mordanted;  and 
this  you  proceed  to  do  by  transferring  the  section  to  the  watch - 


PIG.  19.    DIAGRAM  INDICATING  THE  SUCCESSIVE  STEPS  ix  STAINING  WITH 
BORAX-CARMINE  . 

glass  containing  acid  alcohol.  Notice  the  change  in  color,  from  a 
dull  red  to  a  bright  crimson,  and  when  the  change  is  complete,  lift 
it  into  the  saltcellar  containing  clean  alcohol.  This  dissolves  out 
the  acid.  Five  minutes  suffice  for  this  washing,  after  which  trans- 
fer to  the  oil  of  cloves. 

This  process  does  not  give  as  sharp  contrasts  as  the  hgematoxy- 
lin  and  eosin,  but  it  is  simpler  and  very  permanent.  It  is  best 
to  select  some  one  process  for  general  work,  and  adhere  to  it. 
The  acid  of  the  carmine  process  must  be  guarded  with  extreme 
care,  as  the  smallest  particle  is  sufficient  to  spoil  the  haematoxylin 
solution.  Look  to  it  that  the  dishes  are  kept  scrupulously  clean, 
and  the  sanje  care  must  be  bestowed  upon  the  needles,  forceps, 
and  all  other  instruments. 

Picro- carmine  may  be  used  instead  of  borax -carmine.  The 
sections  may  need  to  remain  in  picro- carmine  as  much  as  an  hour 
to  become  thoroughly  stained.  Acid  alcohol  is  not  to  be  em- 
ployed after  staining.  In  dehydrating,  it  is  well  to  add  some 
picric  acid  to  the  alcohol,  in  order  to  prevent  extracting  the  yel- 
low stain  from  the  specimen. 

You  may,  of  course,  stain  several  sections  at  once,  providing 
you  take  care  to  keep  them  from  rolling  up  or  sticking  together. 

While  the  vessels  which  we  have  recommended  will  be  found  of 
convenient,  proportionate,  and  economical  size  for  general  work, 
larger  ones  are  sometimes  needed  ;  and  almost  any  glass  or  porce- 
lain vessel  may  be  impressed  for  duty. 


CLEANING    SLIDES— TRANSFERRING    SECTIONS 


41 


MOUNTING    OBJECTS 
CLEANING     SLIDES    AND     COVERS 

When  purchasing  slides,  let  us  urge  you  to  get  them  of  goad 
quality.  The  regular  size  is  one  by  three  inches,  and  the  edges 
should  be  smoothed.  As  furnished  by  the  dealers  they  are  usually 
quite  clean,  and  only  require  rubbing  with  a  piece  of  old  linen  to 
prepare  them  for  use. 

The  cover -glasses  should  be  thin,  not  over  TO~O  of  an  inch, 
called  in  the  trade -lists  "No.  1."  Circles  or  squares  three-quarters 
of  an  inch  in  diameter  are  generally  convenient.  They  must  be 
thoroughly  cleaned.  Drop  them  singly  into  a  saucer  containing 
hydrochloric  acid.  Then  pour  off  the  acid,  and  let  clean  water  run 
into  the  dish  for  several  minutes.  Drain  off  the  water  and  pour 
a  little  alcohol  on  the  covers.  Remove  them  one  at  a  time  with  the 
forceps  or  needle,  and  wipe  dry  with  old  linen.*  The  glass  may 
be  held  between  the  thumb  and  forefinger,  the  linen  being  inter- 
posed. Very  slight  pressure  and  rubbing  will  complete  the  process. 
The  surface  of  the  glasses  should  be  brilliant,  and  they  should 
be  preserved  for  future  use  in  a  dust -tight  box. 


TRANSFERRING    THE     SECTIONS    TO    THE     SLIDE 

The  section  is  to  be  taken  from  the  oil  with  a  section -lifter  or 
spatula,  Fig.  20.  Smooth,  stiff  paper,  cut  in  strips,  may  be  used  in 
the  same  wav. 


FIG.  20.     SECTION-LIFTERS. 


In  changing  the  sections  on  the  needle  or  spatula  from  one  fluid 
to  another,  as  from  alcohol  to  oil  of  cloves,  it  is  well  to  touch  the 


*We  are  indebted  to  Professor  Gage,  of  Cornell  University,  for  suggesting  the  use  of  Japanese 
tissue-paper  for  wiping  cover-glasses,  lenses,  etc.  Ordinary  manilla  toilet-paper  is  also  an  excel- 
lent material  for  such  work. 


42 


STUDENTS   HISTOLOGY 


edge  of  the  section  to  a  sheet  of  blotting-paper  or  filter- paper,  to 
remove  as  much  as  possible  of  the  first  fluid  and  prevent  its  dilut- 
ing the  second. 

Place  a  clean  slide  on  the  table  before  you,  and,  with  the  section- 
lifter  used  like  a  spoon,  dip  up  one  of  the  sections  from  the  clove 
oil.  By  inclining  the  lifter,  the  section  may  be  made  to  float  to 


FIG.  21.  METHOD  OF  LABELING  A  MOUNTED  SPECIMEN. 

the  center  of  the  slide.  A  small  sable  brush  is  often  convenient 
for  coaxing  the  section  off  the  lifter. 

If  it  were  our  present  object  to  simply  examine  the  section,  we 
could  drop  a  thin  cover -glass  on  the  specimen,  and  it  would  be 
ready  for  study.  Such  an  object  would  afford  every  requirement 
for  present  observation,  but  would  not  be  permanent.  The  oil  of 
cloves  would  evaporate  after  a  few  days,  and  the  section  be  ruined. 
We  proceed  to  make  a  permanent  mounting  of  our  object. 

The  clove  oil  surrounding  the  section  on  the  slide  is  first  to  be 
removed,  and  it  can  easily  be  done  by  means  of  blotting-paper. 
With  a  narrow  slip  of  thin  filter -paper  wipe  up  the  oil,  exercising 
care  not  to  touch  the  section,  or  it  will  become  torn.  Proceed  care- 
fully, taking  fresh  paper  until  the  oil  will  no  longer  drain  from  the 


FIG.  22.     MODE  OF  HANDLING  THE  COVER-GLASS  IN  MOUNTING 
TISSUES— FREEBORN. 

section  when  the  slide  is  held  vertically.  With  a  glass  rod  remove 
a  little  of  the  xylol  balsam  (vide  formulae)  from  the  bottle,  and 
allow  a  drop  of  this  balsam  to  fall  upon  the  section. 

Pick  up  a  clean  cover- glass  with  the  forceps,  and  place  it  on 
the  drop  of  balsam.     This  operation  is  seen  in  Fig.  22.     The  point 


CARE    OF   THE   MICROSCOPE  43 

of  the  forceps  may  be  placed  beneath  the  cover -glass,  the  tip  of  the 
forefinger  pressing  lightly  over  it,  and  you  will  be  enabled  to  carry 
the  thin  glass  wherever  desired. 

As  the  cover  settles  down  the  air  is  pressed  out,  until  finally  the 
section  appears  imbedded  in  the  varnish — the  latter  filling  the  space 
between  the  cover  and  the  slide. 

The  object  is  "mounted."  You  have  a  permanent  specimen. 
The  slide  must  be  kept  flat,  as  the  balsam  is  soft.  After  some 
weeks,  the  varnish  around  the  edges  of  the  cover  will  stiffen,  and 
eventually  become  solid.  Do  not  paint  colored  rings  around  the 
specimen.  Nothing  can  present  a  neater  appearance  than  the 
simple  mount,  as  we  have  described  it,  after  having  been  properly 
labeled.  Labels  seven -eighths  of  an  inch  square  may  be  put  on 
one  or  both  ends,  with  the  name  of  the  object,  date,  method  of 
staining,  or  whatever  particulars  you  may  prefer. 

Specimens  should  be  kept  in  trays  or  boxes  in  such  manner  that 
they  may  always  lie  flat. 

CARE    OF   THE   MICROSCOPE 

The  objectives  constitute  the  most  valuable  part  of  the  instru- 
ment. The  lenses  should  never  be  touched  with  the  fingers;  indeed, 
the  same  rule  applies  to  all  optical  surfaces.  When  the  glasses 
become  soiled  they  may  be  cleaned,  but  it  should  be  done  with 
great  care.  While  the  effect  of  a  single  cleaning  would  probably 
not  be  of  the  slightest  appreciable  injury  to  the  glass,  repeated 
wiping  writh  any  material,  however  soft,  will  destroy  the  perfect 
polish,  and  result  in  obstruction  of  light  and  consequent  dimness  in 
the  field.  Never  use  a  chamois  leather  on  an  optical  surface,  as 
these  skins  contain  gritty  particles.  Old,  well  worn  linen  and 
Japanese  paper  are  by  far  the  best  materials  for  wiping  glasses.  If 
a  lens  be  covered  with  dust,  brush  it  off,  breathe  on  the  surface, 
and  wipe  gently  with  the  linen  or  paper.  Should  you  get  clove  oil 
on  the  front  lens  of  the  objective  (as  frequently  happens  when 
examining  temporary  mounts)  wipe  it  dry,  and  then  clean  with  the 
linen  moistened  with  a  drop  of  alcohol.  Canada  balsam  can  be 
very  readily  removed  from  any  surface  after  having  softened  it  with 
oil  of  cloves.  The  front  lens  of  the  objective,  being  the  only  one 
exposed,  is  the  one  usually  soiled. 

Particles  of  dirt  on  the  objective,  as  I  have  said,  cause  a  dim- 
ness in  the  field — the  image  is  blurred.  Dust  on  the  lenses  of  the 


44  STUDENTS   HISTOLOGY 

eye -piece,  however,  appears  in  the  field.  These  lenses  are  readily 
cleaned  by  dusting  and  wiping  with  the  linen,  after  having  breathed 
on  the  surface.  Never  wipe  a  lens  when  dusting  with  a  cam  el' s- 
hair  brush  will  answer  the  purpose. 

The  microscope  should  either  be  covered  with  a  shade  or  cloth, 
or  put  away  in  its  case  when  not  in  use.  The  delicate  mechanism 
of  the  fine  adjustment  becomes  worn  and  shaky  if  not  kept  free 
from  dirt. 


PAKT   SECOND 
STRUCTURAL    ELEMENTS 


PRELIMINARY  STUDY 
FORM     OF     OBJECTS 

From  a  single  and  hasty  view  of  bodies  under  the  microscope, 
we  are  liable  to  form  erroneous  ideas  of  form.  Either  a  sphere, 
disc,  ellipsoid,  ovoid,  or  cone  may  be  so  viewed  as  to  present  a 
circular  outline.  It  therefore  becomes  important  to  view  objects  in 
more  than  a  single  position.  This  can  easily  be  accomplished  with 
isolated  particles  by  suspension  in  a  liquid.  In  this  way  the  true 
shape  of  a  blood -corpuscle,  e.g.,  may  be  determined. 

Again,  much  information  concerning  the  actual  form  of  bodies 
may  be  gained  by  a  proper  adjustment  of  the  fine  focusing  screw. 
You  maj'  remember  that  the  depth  of  the  field  of  view  in  the  micro- 
scope is  exceedingly  slight.  Speaking  accurately,  only  a  single 
plane  can  be  seen  with  a  single  focal  adjustment  ;  but  by  gradually 
raising  or  lowering  the  t  tube  of  the  microscope  the  different  parts 
of  a  body  may  be  focused  and  studied,  and  an  accurate  idea  of 
form  secured. 

With  a  glass  rod  place  a  drop  of  milk,  which  has  been  pre- 
viously diluted  with  three  parts  of  water,  on  a  slide,  and  put  a  cover- 
glass  thereon,  as  in  Fig.  23.  Focus  first  with  the  low-power  (L). 
A  multitude  of  minute  dots  are  observed.  Then  change  to  the  high- 
power  (H),  and  the  dots  will  resolve  into  circular  figures.  Select 
one  of  the  smaller  particles,  and,  as  you  raise  the  focus,  the  center 
of  the  figure  retains  its  brilliancy,  while  the  edges  become  dark  or 
blurred,  showing  convexity.  Reverse  the  focus,  and  the  center 
again  retains  its  sharpness  long  after  the  edge  has  become  blurred. 
The  figure,  then,  is  a  spheroid.  These  bodies  are  fat -globules. 
Particles  of  free  fat  always  assume  the  spheroidal  form  when  sus- 
pended in  a  liquid. 

(45) 


46  STUDENTS   HISTOLOGY 

Note  the  larger  globules:  they  have  become  flattened  by  the 
pressure  of  the  cover -glass. 

Clean  the  slide,  and  make  a  second  preparation  from  the  diluted 
milk — first,  however,  shaking  it  violently  in  a  bottle.  Note  the 
flattened  air -bubbles  among  the  oil -globules.  Observe  that  these 
air -bubbles  have  no  intrinsic  color,  while  the  fat -globules  are 


A  | 


FIG.  23.     DIAGRAM  SHOWING  THE  EFFECT  OF  AIR-BUBBLES  AND  OIL-GLOBULES 
IN  A  MOUNTED  SPECIMEN  UPON  THE  RAYS  OF  LIGHT. 

The  lines  A,  B  show  the  refraction  of  the  rays  (so  as  to  produce  a  ring  of  color)  by  the  action 
of  two  plano-concave  water-lenses  which  are  formed  by  the  air-bubble. 

The  oil  is  seen  to  correct  the  refraction  of  C,  D,  thus  giving  but  little  color  to  the  margin  of 
this  globule. 

faintly  yellow.  Observe  the  change  in  the  ring  of  prismatic  color 
about  the  edge  of  the  air -bubble,  as  the  focus  is  altered.  No  such 
color  will  be  seen  in  connection  with  the  oil -globule. 

The  bubbles  assume  various  figures  from  the  pressure  of  the 
cover- glass. 

MOVEMENT     OF     OBJECTS 

Objects  are  frequently  seen  moving  in  the  field  of  the  micro- 
scope, the  movement  being  magnified  equally  with  their  dimen- 
sions. 

Thermal  Currents. — When,  with  the  previous  specimen  or  any 
other  fluid  mount,  the  warm  hand  is  brought  close  to  one  side  of 
the  stage,  the  globules  in  the  field  will  be  seen  swimming  more  or 
less  rapidly.  These  currents  are  due  to  the  unequal  heating  of  the 
liquid  under  observation.  The  direction  of  the  current  is  in  the 
reverse  of  its  apparent  motion. 

Brownian  Movement. — Place  a  fragment  of  dry  carmine  on  a 
slide,  add  a  drop  of  water,  and  with  a  needle  stir  until  a  paste  is 
formed.  Add  another  drop  of  water,  and  immediately  put  on  the 
cover -glass.  With  H,  note  the  most  minute  particles,  and  observe 
their  peculiar,  dancing  motion.  This  occurs  when  almost  any 
finely  divided  and  generally  insoluble  solid  is  mixed  with  water.  It 


EXTRANEOUS    SUBSTANCES 


47 


ceases  after  a  short  time.  The  movement  has  been  attributed  to 
several  causes. 

Vital  Movements. — Place  a  drop  of  decomposing  urine  on  a 
slide,  cover,  and  focus  with  H.  The  field  contains  innumerable 
minute  spherules  and  rods  (bacteria)  which  are  in  active  motion, 
resembling  somewhat  the  Brownian  movement,  although  sufficiently 
distinctive  after  close  observation. 

After  having  rubbed  the  tongue  for  a  moment  against  the  inner 
surface  of  the  cheek,  put  a  drop  of  saliva  on  a  slide,  cover,  and 
focus  (H) .  Among  the  numerous  thin,  nucleated  scales  and  debris, 
small  granular  spherules — the  salivary  corpuscles — will  be  found. 
Select  one  of  the  last,  center,  and  focus  (H)  with  extreme  care.  The 
minute  granules  within  the  cells  are  in  active  motion,  resembling 
the  Brownian  movement,  but  with  proper  conditions  the  motion 
may  continue  for  many  hours. 

EXTRANEOUS     SUBSTANCES 

Before  we  begin  the  study  of  animal  tissues,  we  wish  to  have  you 
become  somewhat  familiar  with  the  appearance  of  certain  objects 


FIG.  24.     EXTRANEOUS  SUBSTANCES. 

A.  Cotton  fibers,  showing  the  characteristic  twist. 

B.  Linen  fibers,  with  transverse  markings,  indicating  segments. 

C.  Wool.     The  irregular  markings  are  produced  by  the  overlapping  of  flattened  cells.     Wool 
may  be  distinguished  from  other  hairs  by  the  swellings  which  appear  at  irregular  intervals  in  the 
course  of  the  former. 

D.  Silk.     Smooth  and  cylindrical. 


48 


STUDENTS   HISTOLOGY 


which  are  frequently,  through  accident  or  carelessness,  and  often 
in  spite  of  the  utmost  care,  found  mixed  with  our  microscopical 
specimens.  Among  the  more  common  objects  floating  in  the  air 
and  gaining  access  to  reagents,  to  subsequently  appear  in  our 
mounted  specimens,  are  the  following  : 

Fibers. — Procure  minute  pieces  of  uncolored  linen,  cotton,  wool, 
and  silk.  With  a  needle  in  either  hand,  tease  out  or  separate  a  few 
fibers  on  slides,  add  a  drop  of  water,  and  cover.* 


FIG.  25.     EXTRANEOUS  SUBSTANCES. 

A.  Granules  of  potato  starch. 

B.  Corn  starch. 

C.  Wood  fibers.     The  circular  dots  are  peculiar  to  the  tissue  of  cone-bearing  trees. 

D.  Spiral  thread  from  a  tea  leaf. 

E.  Fragment  of  feather. 

F.  Cells  of  yeast  and  mould. 

Starch. — Procure  samples  of  wheat,  corn,  potato,  and  arrow-root 
starch,  or  scrape  materials  containing  any  one  of  these  substances 
with  a  sharp  knife.  To  a  minute  portion  on  the  slide  add  a  drop 
of  water,  cover,  and  examine  with  L  and  H. 

Wood  Shavings,  Feathers,  Minnie  Insects,  Portions  of  Larger 
Insects,  Pollen,  etc.,  are  easily  mounted  temporarily  or  permanently, 

These  substances,  as  well  as  most  of  those  which  follow  under  the  same  heading,  may  be 
mounted  permanently  as  follows:  Put  the  dry  material  in  clean  turpentine  for  a  day  or  two,  to 
remove  the  contained  air.  Transfer  to  the  slide,  tease,  separate,  or  arrange  the  elements,  after 
which  wipe  away  the  turpentine  with  strips  of  blotting-paper.  Add  a  drop  of  balsam,  and  place 
the  cover-glass  thereon.  The  weight  of  the  cover  will  be  sufficient  to  press  the  object  flat,  if  it  be 
properly  teased  or  separated. 


STRUCTURAL    ELEMENTS— CELLS  49 

as  before  noted.  They  are  very  commonly  found  in  urine 
after  it  has  been  exposed  to  the  air,  and  their  recognition  is 
very  important. 

Let  me  urge  you  to  become  familiar  with  the  microscopical^ 
appearance  of  the  commoner  objects  which  surround  us  in  every- 
day life.  The  most  serious  mistakes  have  resulted  from  ignorance 
of  this  subject.  Vegetable  fibers  have  been  mistaken  for  nerves 
and  urinary  casts,  starch  granules  for  cells,  vegetable  spores  for 
parasitic  ova,  etc. 


STRUCTURAL    ELEMENTS 

Certain  anatomical  structures,  of  a  more  or  less  elementary 
nature,  are  united  in  the  composition  of  organs.  These  structural 
elements  will,  with  propriety,  first  claim  notice  from  us. 


CELLS 


A  typical  cell  is  a  microscopical  sphere  of  protoplasm,  consti- 
tuted as  follows  (vide  Fig.  26) : 

A.  Limiting  membrane. 

B.  Cell-body. 

C.  Nucleus. 

D.  Nucleolus. 


D 

FIG.  20.    ELEMENTS  OF  A  TYPICAL  CELL. 

The  wall  consists  of  an  apparently  structureless  membrane  of 
extreme  tenuity. 

The  cell-body  may  be  either  clear  (jelly-like),  granular,  or 
fibrilliated.  It  contains  an  albuminous  substance  called  protoplasm. 

The  nucleus  is  a  minute  spherical  vesicle,  with  a  limiting  mem- 
D 


50  STUDENTS   HISTOLOGY 

brane  inclosing  a  clear  gelatinous  material,  traversed  by  a  reticulum 
of  fibrillae. 

The  nucleolus  consists  of  a  spherical,  highly  refracting  body 
lying  inside  of  the  nucleus,  sometimes  appearing  to  be  a  granular 
enlargement  upon  the  fibrillas  of  the  nucleus. 

Deviations  from  the  type  are  most  frequent,  and  vary  greatly  as 
to  form,  number  of  elements,  and  chemical  composition. 


FIG.  27.    A  CELL,  NUCLEUS,  WITH  NETWORK  AND 
NUCLEOLUS.    DIAGRAMMATIC. 

The  typically  perfect  cell  is  rarely  seen  in.  human  tissue  on 
account  of  the  length  of  time  which  commonly  elapses  between 
death  and  observation  of  the  structure,  the  delicate  fibrillae  of  the 
nuclei  usually  appearing  as  a  mass  of  granules. 

CELL    DISTRIBUTION 

The  complex  mechanism  of  the  body  had  its  origin  in  a  single 
cell.  This  preliminary  structure,  endowed  with  the  power  of  pro- 
liferation, became  two  cells.  Two  having  been  produced,  they 
became  four:  the  four,  eight ;  and  thus  progression  advanced  until 
they  became  countless.  Some  of  these  cells  remained  as  such; 
others,  altered  in  form  and  composition,  gave  birth  to  muscle,  bone, 
etc.  The  study  of  these  processes  belongs  to  physiology. 

The  adult  body  is  composed  largely  of  cells  of  various  forms. 
The  different  physiological  processes,  as  secretion,  absorption,  res- 
piration, etc.,  are  effected  through  the  intervention  of  these 
anatomical  elements. 

All  free  surfaces,  within  or  without  the  body,  are  covered  with 
cells.  The  entire  skin,  the  outside  of  organs,  as  the  lungs, 
liver,  stomach,  intestines,  brain,  etc.;  all  cavities,  as  the  alimen- 
tary tract,  heart,  ventricles  of  the  brain,  blood-vessels  and  ducts, 
present  a  superficial  layer  of  cells. 

The  cells  are  held  together  by  an  intercellular  substance,  which 
may  be  so  abundant  that  the  cells  form  a  comparatively  small  part 
of  the  tissue.  The  intercellular  material  is  to  be  regarded  as  hav- 


KAETOKINESIS 


51 


ing  been  made  by  the  cells.  In  the  case  of  the  connective  tissues, 
it  has  a  more  important  function  than  the  cells;  while  the  amount 
of  intercellular  substance  in  epithelial  structures  is  trifling. 

CELL -DIVISION 

The  increase  in  the  number  of  cells  in  the  body  may  be  accom- 
plished in  two  ways: 

a.  By  direct  division. 

b.  By  indirect  division. 

Direct  division  is  a  process  in  which  the   cell  becomes   con- 
stricted and  a  portion  of  it  separated  from  the  remainder.     It  is 


FIG.  28.    INDIRECT  CELL-DIVISION— AFTER  FLEMMING. 

now  believed  that  in  most  instances  the  separation  of  the  proto- 
plasm is  preceded  by  a  series  of  changes  in  the  nucleus.  This  mode 
of  division  is  called  indirect.  The  changes  in  the  nucleus  go  by 
the  name  of  karyokinesis,  or  mitosis. 


KARYOKINESIS 

The  reticulum  of  fibers  already  mentioned  as  traversing  the 
substance  of  the  nucleus  has  an  affinity  for  nuclear  stains,  and 
its  substance  is  therefore  called  chromatin.  During  karyokinesis 
the  chromatin  of  the  nucleus  undergoes  a  series  of  complicated 
changes,  resulting  in  its  division  into  two  equal  parts.  This  is 
followed  by  the  division  of  the  rest  of  the  cell.  During  the  process 
the  chromatin  presents  figures  of  great  variety  and  intricacy. 


52 


STUDENTS   HISTOLOGY 


The  effect  of  these  changes  is  to  separate  the  chromatin  into 
masses  called  chromosomes.  The  number  of  chromosomes  varies  in 
different  species,  but  is  probably  constant  in  the  same  species. 
Fig.  29  shows  the  main  events  in  karyokinesis  in  a  diagrammatic 
manner.  It  represents  the  process  as  it  occurs  in  the  starfish, 
where  the  process  is  less  complicated  than  in  some  cases.  Each 


C  D 

FIG.  29.     KARYOKINESIS— AFTER  WILSON. 


chromosome  becomes  split  lengthwise  into  two  halves.  One  group 
of  halves  moves  to  one  end  or  pole  of  the  cell,  the  other  group  to 
the  other  pole.  The  two  groups  of  chromosomes  give  rise  to  two 
new  nuclei. 

The  separation  of  the  groups  of  chromosomes  is  accomplished 
by  delicate  filaments,  which  radiate  from  the  two  poles  to  which  the 
chromosomes  are  to  travel.  Some  of  these  filaments  meet  at  the 
equator  of  the  cell  to  form  what  is  called  the  nuclear  spindle.  The 


CLASSIFICATION  OF   TISSUES 


53 


radiating  filaments  at  the  poles  of  the  cells  present  figures  which 
have  been  compared  by  Wilson  to  the  arrangement  of  iron  filings 
about  the  poles  of  a  horseshoe  magnet.  The  circle  of  radiating 
filaments  at  each  pole  is  called  the  attraction- sphere,  the  center  of 
which  is  the  centrosome.  It  is  possible  that  the  substance  of  the 
filaments  serves  to  draw  the  chromosomes  apart.  Apparently  the 
centrosome  is  to  be  regarded  as  a  permanent  organ  of  the  cell. 
Its  division  must  precede  the  division  of  the  nucleus. 

The  time  required  for  cell  division  in  man  is  about  half  an 
hour  (Stohr). 

Most  of  the  stages  in  karyokinesis  may  be  demonstrated  in  the  epithelial 
cells  in  the  tail  of  a  young  newt  or  salamander  tadpole.  Fix  in  Flemming's 
osmie  acid  or  chromic -acetic  solution  for  twenty-four  hours;  wash;  stain  with 
safranin  or  hsematoxylin ;  and,  after  dehydrating  and  clearing,  mount  in  balsam. 
Examine  with  oil -immersion  lens,  if  possible. 


CLASSIFICATION   OF   TISSUES 

Histology,  or  microscopical  anatomy,  treats  of  the  minute 
structure  of  the  tissues  and  organs  of  the  body. 

A  tissue  is  a  collection  of  similar  cells  and  intercellular  sub- 
stances. The  principal  tissues  are  epithelial,  connective,  muscular, 
and  nervous.  Blood  is  sometimes  considered  as  a  tissue.  Most 
organs  are  made  of  several  different  tissues. /The  following  table 
shows  the  varieties  of  tissues:  / 


Epiilielial  Tissue  { 
<• 


Connective  Tissue 


Columnar. 
Endothelium. 
Blood. 

Mucoid. 

White  Fibrous. 

Yellow  Elastic. 

Adipose. 

Retiform  (of  lymphoid  tissue), 

Cartilaginous. 

Osseous. 
L  Dentine. 

{Unstriated. 
Striated. 
Cardiac. 
Nervous  Tissue. 


54 


STUDENTS   HISTOLOGY 


Ectoderm 

or 
Epiblast 


EMBRYONIC     DERIVATION     OP     TISSUES 

In  correlating  the  work  of  histology  with  that  of  embryology, 
the  student  will  find  the  following  table  serviceable.  The  table 
indicates  from  which  layer  of  the  blastoderm  each  of  the  prin- 
cipal tissues  is  derived: 

The  epithelium  of  the  skin  and  all  its  appendages  and  glands. 

The  epithelium  covering  the  front  of  the  eye,  the  crystalline  lens, 
and  the  retina. 

The  epithelium  of  the  external  auditory  canal  and  of  the  mem- 
braneous labyrinth. 

The  epithelium  of  the  nasal  cavity  and  its  diverticula. 

The  epithelium  of  the  mouth  and  its  glands,  the  salivary  glands, 
and  the  enamel  of  the  teeth. 

The  epithelium  of  the  anal  end  of  the  alimentary  canal. 

The  tissues  of  the  nervous  system,  the  lining  of  the  central  canal 
of  the  spinal  cord  and  of  the  cerebral  ventricles,  the  pituitary 
and  pineal  bodies. 

All  connective  tissues. 
Muscular  tissue. 

The  blood- and  lymph-vessels  and  their  endothelium,  and  the  endo- 
Mesoderm  thelium  of  the  serous  membranes. 

or         <  Blood -and  lymph-'corpuscles. 
Mesollast      The  spleen  and  lymph -nodes. 
The  kidney  and  ureter. 

The  ovary  and  testicle  and  their  ducts,  except  the  external  ends  of 
the  ducts. 

The  epithelium  of  the  alimentary  canal  (except  at  the  upper  and 
lower  extremities),  and  all  the  glands  opening  into  it,  includ- 
Entoderm  ing  the  liver,  pancreas,  thyroid,  and  thymus. 

or  -s  The  epithelium  of  the  respiratory  tract  which  originates  as  a 
Jlypoblast  diverticulum  from  the  alimentary  canal. 

The  epithelium  of  the  Eustachian  tube  and  tympanum. 
The  epithelium  of  the  urinary  bladder  and  urethra. 


EPITHELIUM 

Epithelium  is  the  tissue  covering  the  surfaces  of  the  body  that 
V/    communicate  with  the  external  world,  and  lining  the  glands.*     It 
is    made   of    cells,    held    together    by   only   a    small    amount    of 
intercellular  substance. 


*Note  the  exceptions  in  the  case  of  the  peritoneum,  which  is  lined  by  endothelium,  and  which 
opens  externally  by  means  of  the  Fallopian  tube;  the  thymus  and  thyroid  glands,  and  the 
cavity  of  the  central  nervous  system,  which  contain  or  are  lined  by  epithelium,  but  do  not  open 
externally. 


SQUAMOUS,  STRATIFIED,  AND  TRANSITIONAL  EPITHELIUM     55 


Where  a  layer  of  epithelial  cells  comes  in  contact  with  the 
underlying  connective  tissue,  the  deepest  epithelial  cells  often  rest 
upon  a  thin  basement  membrane,  which  is  modified  connective 
tissue,  either  structureless  or  made  of  flattened  cells. 

The  succeeding  pages  will  show  that  epithelial  cells  may  £e 
squamous  or  columnar,  ciliated  or  otherwise,  simple  or  stratified. 
These  varieties  of  epithelium  are  distributed  as  follows,  giving  cinly 
their  most  important  locations: 


Simple 
Squamous 
Epithelium 


Stratified 
Squamous 
Epithelium 


Simple 
Columnar 
Epithelium 


Stratified 
Columnar 
Epithelium 


The  alveoli  of  the  lungs. 

The  capsule  of  the  Malpighian  body  and  the  descending  limb  of 
the  loop  of  Henle  in  the  kidney. 

The  covering  of  the  skin,  of  the  eye,  mouth  and  tongue, 
pharynx,  oesophagus,  epiglottis,  and  of  the  upper  part  of 
the  larynx. 

The  lining  of  the  urinary  tract  from  the  pelvis  of  the  kidney 
down  (except  part  of  the  male  urethra),  most  of  it  being 
of  the  special  variety  of  stratified  squamous  epithelium 
known  as  transitional. 

The  lining  of  the  vagina. 

The  alimentary  canal  from  the  beginning  of  the  stomach  to  the 
lower  part  of  the  rectum;  the  ducts  of  its  glands  and  of 
many  other  glands;  the  seminal  vesicles,  ejaculatory  ducts, 
and  part  of  the  male  urethra;  the  surface  of  the  ovary. 

It  is  ciliated  in  the  uterus  and  Fallopian  tube,  the  central  canal 
of  the  spinal  cord,  and  the  cerebral  ventricles. 

It  is  ciliated  in  the  most  important  situations:  The  trachea 
and  bronchial  tubes,  the  Eustachian  tube,  the  upper  part  of 
the  pharynx,  the  lower  part  of  the  nasal  cavity,  the  vas 
deferens. 


SQUAMOUS,    STRATIFIED,    AND     TRANSITIONAL    EPITHELIUM 


The  simplest  method  of  tissue  production  by  means  of  flat  cells 
is  that  of  superposition,  constituting  squamous  epithelium.  Cells 
are  placed  one  over  the  other,  generally  without  great  regularity. 
If  regular,  and  in  several  layers,  the  structure  is  called  stratified 
epithelium;  if  only  in  a  few  layers,  it  is  termed  transitional  epithe- 
lium. The  superficial  layer  of  the  skin  affords  an  example  of 
squamous,  stratified  epithelium.  The  bladder  and  pelvis  of  the 
kidney  are  lined  with  transitional  epithelium. 

The  thin,  flat  .scales  from  the  mouth  may  be  demonstrated  by 
scraping  a  drop  of  saliva  from  the  tongue  with  the  handle  of  a 
scalpel,  transferring  it  to  the  slide,  and  applying  the  cover.  The 


56 


STUDENTS   HISTOLOGY 


size  of  the  drop  of  saliva  should  be  carefully  adjusted  so  as  to  fill 
the  space  between  the  cover- glass  and  slide.  Too  little  will  cause 
the  cover  to  adhere  so  tightly  to  the  slide  as  to  press  the  cells  out 
of  form;  too  much,  and  the  saliva  flows  over  the  cover  and  soils 
the  objective.  With  a  glass  rod  place  a  drop  of  the  dilute  eosin 
solution  on  the  slide,  and  with  a  needle  lead  it  to  the  edge  of  the 
saliva.  The  dye  will  pass  under  the  cover  slowly,  and  whatever 
anatomical  elements  there  may  be  present  will  be  gradually  stained. 
Observe  that  the  nuclei  of  the  flat  scales  first  take  the  dye  and 
appear  of  a  deep  pink;  while  the  other  portions  are  either  colorless 
or  very  lightly  stained. 

Find  a  typical  field  and  sketch  it  with  a  pencil,  afterward  tint- 
ing with  dilute  eosin. 

An  admirable  view  of  the  surface  of  a  squamous  epithelium  may 
be  had  by  using  the  superficial  layer  of  the  skin  of  a  frog,  which  is 


FIG.  30.     SQUAMOUS  EPITHELIAL,  CELLS  FROM  THE  MOUTH. 

often  shed  when  the  animal  is  kept  in  confinement.  It  may  be 
stained  with  haematoxylin;  and  small  pieces,  after  alcohol  and 
clearing,  may  be  mounted  in  balsam. 


PAVEMENT     EPITHELIUM 


When  thin,  flat  cells  are  disposed  in  a  single  layer,  like  tiles, 
the  epithelium  is  termed  simple  squamous,  pavement,  or  tessellated. 
These  cells  are  often  quite  regularly  polygonal  (although  this 


COLUMNAR    EPITHELIUM 


57 


obtains  more  frequently  with  tissue  from  the  lower  animals),  and 
they  are  always  connected  by  their  edges  by  means  of  an  albumi- 
nous cement. 

Such   a  simple  squamous  epithelium  is  found  in   only  a  few 
locations.     The  most  important  are  the  alveoli  of  the  lungs,  the 


FIG.  31.     PAVEMENT  EPITHELIUM.     DIAGRAMMATIC. 

capsule  of  the  Malpighian  body  of  the  kidney,  and  the  descending 
limb  of  the  loop  of  Henle  in  the  kidney.  Seen  from  the  surface, 
a  stratified  or  columnar  epithelium  appears  like  pavement  epithe- 
lium. 


COLUMNAR     EPITHELIUM 

Columnar  cells  are  found,  generally,  throughout  the  alimentary 
and  respiratory  tracts,  except  near  their  external  openings.  They 
also  line  the  cerebral  ventricles,  most  of  the  uriniferous  tubules, 
Fallopian  tubes,  the  uterus,  etc.  This  epithelium  is  quickly  de- 
stroyed after  death,  and  is  difficult  of  perfect  demonstration, 
except  in  an  animal  recently  killed. 

Procure  from  the  abattoir  a  portion  of  the  small  intestine  and 
bronchus  of  a  pig,  and  with  the  curved  scissors  snip  out  small 
pieces  from  the  mucous  surface  of  each.  Macerate  in  one-sixth  per 
cent,  of  chromic  acid  for  twenty -four  hours. 

Place  a  piece  of  the  gut  on  a  slide,  and,  after  having  added  a 
drop  of  the  acid  solution,  scrape  off  the  mucous  surface  with  a  knife 
and  remove  the  remainder  of  the  gut.  Add  a  cover -glass,  and 
focus  (H).  You  will  find  cells  in  various  conditions,  from  isolated 
examples  to  small  groups  like  Fig.  32. 

Observe  that  the  attached  ends  of  the  cells  are  often  small  and 


58 


STUDENTS   HISTOLOGY 


pointed,  and  that  spheroidal  and  ovoidal  cells  are  frequently  wedged 
in  between  them.     Note  the  free  border:    it  consists  of  striae,  and 


PIG.  32.     COLUMNAR  CELLS  FROM  SMALL  INTESTINE  OF  RABBIT. 

A.  Tapering  attached  extremity. 

B.  A  swollen  goblet  cell. 

C.  Finely  striated  free  border. 

D.  Transparent  line  of  union  between  the  striated  portion  and  the  body  of  the  cell  (X  400). 

is  separated  from  the  body  of  the  cell  by  a  translucent  line.     This 
appearance  is  also  that  of  the  epithelium  in  the  human  intestine. 


PIG.  33.     CILIATED  COLUMNAR  CELLS  FROM  BRONCHUS  OF  PIG  (X  400). 

Ciliated    Columnar   Epithelium 

Prepare,  by  scraping,  a  slide  from  the  mucous  surface  of  the 
pig's  bronchus  (which  has  been  macerating  in  the  chromic  acid) 


GLANDULAR    EPITHELIUM 


59 


Observe  the  cilia  on  the  free  border  of  the  cells.  Interspersed 
between  ciliated  cells,  much -enlarged  individuals  may  be  found — 
the  so-called  beaker,  goblet,  or  mucous  cells. 

The  motion  of  the  cilia  may  be  demonstrated  as  follows: 
Carefully  open  an  oyster  so  as  to  preserve  the  fluid.     On  exam- 
ination  you   will  notice  the  gills,  shown  in   Fig..  34,  commonly 


FIG.  34.     OYSTER,  OPENED  TO  SHOW  METHOD  OF  PROCURING  LIVING  CILIATED  CELLS. 

A.  The  divided  muscle.    This  must  be  sectioned  before  the  shell  can  be  opened 

B.  The  heart. 
0.  Liver. 

D,  D.  The  so-called  "beard."  These  laminae  are  covered  with  cells  provided  with  cilia;  and 
a  fragment  of  the  free  border  of  one  of  the  leaflets  may  be  snipped  off  with  the  scissors  and 
examined  as  described  in  the  text. 

called  the  beard.  With  the  scissors  snip  off  a  fragment  of  the  free 
border  of  this  beard,  add  a  drop  of  the  liquid  from  the  oyster,  and 
tease  with  a  pair  of  needles.  Apply  the  cover,  and  focus  (H). 

At  first  the  individual  cilia  cannot  be  demonstrated  on  account 
of  their  rapid  vibration.  After  a  few  moments,  however,  the 
action  becomes  less  energetic,  and  the  hair -like  appendages  of  the 
cells  are  to  be  plainly  seen. 


GLANDULAR    EPITHELIUM 

Scrape  the  cut  surface  of  a  piece  of  liver;  place  the  scrapings 
on  a  slide;  add  a  drop  of  normal  salt  solution  (vide  formulae) ;  mix 
with  a  needle,  and  put  on  the  cover -glass. 

With  H  observe,  among  the  numerous  blood -corpuscles,  fat- 
globules,  etc.,  the  polyhedral  liver -cells,  about  twice  or  three  times 
the  diameter  of  a  white  blood -corpuscle  (Fig.  35).  Notice  the 
large  spherical  nuclei,  with  nucleoli.  Note,  also,  the  yellow 


60 


STUDENTS    HISTOLOGY 


FIG.  35.     GLANDULAK  EPITHELIUM. 

A.  A.  Polyhedral  cells  from  human  liver. 

B.  Double  nuclei. 

C.  Cells  from  same  showing  connection  with  a  capillary. 

D.  Same  cells  infiltrated  with  globules  of  fat. 

E.  Cells  from  liver  of  pig  showing  intracellular  network  (X  400). 

pigment -granules  and  the  fat -globules  in  the  body  of  the  cells. 
Masses  of  these  cells  resemble  somewhat  pavement  epithelium ;  they 
are  not  flat,  but  polyhedral. 


ENDOTHELIUM 

Endothelium  resembles  simple  squamous  epithelium  in  appear- 
ance, and  it  is  called  epithelium  by  some  histologists. 

Endothelium  forms  the  superficial  covering  of  the  pleural,  peri- 
cardial,  and  peritoneal  cavities,  the  tunica  vaginalis,  and  the  joints. 
It  covers  the  membranes  of  the  brain  and  spinal  cord,  the  inner 
surfaces  of  the  heart,  and  the  blood-  and  lymphatic  vessels. 
Therefore  endothelium  lines  the  cavities  that  do  not  communicate 
with  the  external  world. * 

It  consists  of  a  single  layer  of  thin,  flat  cells,  held  together  by  a 
small  amount  of  intercellular  substance.  It  is  demonstrated  best 
on  fresh  tissues,  hence  the  human  subject  is  seldom  available. 

The  mesentery  of  the  frog  affords  a  good  example  of  endothelial 


*Remember  that  the  peritoneum  may  be  said  to  have  an  opening  by  way  of  the  Fallopian 
tube,  and  that  the  central  canal  of  the  spinal  cord  and  brain  is  lined  by  epithelium  but  has  no 
opening  that  connects  it  with  the  external  world. 


ENDOTHELIUM 


61 


structure,  and  differs  but  little  from  the  arrangement  on  human 
serous  surfaces. 

Kill  a  large  frog  by  decapitation,  and  open  the  abdomen  freely 
by  an  incision  along  the  median  line.  Pull  out  the  intestines 
grasping  the  stomach  with  the  forceps.  This  will  expose  the  small 
intestine,  which  you  will  remove,  together  with  the  attached  mes- 
entery, by  means  of  quick  snips  of  the  scissors.  Work  as  rapidly 
as  possible  and  avoid  soiling  the  tissue  with  blood.  Throw  the 
gut  into  a  saltcellar  filled  with  silver  solution  (vide  formula), 
where  it  must  remain  for  ten  minutes  covered  from  the  light.  Lift 
the  tissue  from  the  solution  by  means  of  a  strip  of  glass  (or  a 
platinum  wi#e),  and  throw  into  a  saucer  of  clean  (preferably  dis- 
tilled) water,  changing  the  latter  repeatedly  for  some  minutes. 


FIG.  36.    ENDOTHELIUM  PROM  FROG'S  MESENTERY.     SILVER  STAINING. 

A.  Area  showing  the  outlining  of  the  cells  by  the  silver  stained  cement-substance.    The 
nuclei  have  been  brought  out  by  the  carmine.    Minute  stomata  may  be  seen  between  certain 
cells. 

B.  A  blood-capillary  terminating  below  in  an  arteriole.    The  silver  has  outlined  the  endo- 
thelial  cells  of  the  vessels. 

C.  An  area  showing  both  layers  of  the  cells.    The  deeper  cells  are  faintly  outlined,  being 
out  of  focus.    The  silver  has  been  deposited  over  the  lower  portion  of  the  specimen,  nearly 
obscuring  the  cement  lines  (X  250). 


62  STUDENTS   HISTOLOGY 

After  washing,  and  while  yet  in  the  water,  expose  to  sunlight 
(perhaps  fifteen  minutes)  until  a  brown  tint  is  acquired,  which 
indicates  the  proper  staining. 

The  mesentery  has  been  left  connected  with  the  intestine,  so 
that  the  former  might  not  curl.  The  preparation  having  been 
dehydrated  with  alcohol,  and  having  reached  the  oil  of  cloves,  pro- 
ceed with  a  pair  of  scissors  to  snip  off  a  small,  flat  piece  of  mesen- 
tery. Remove  it  to  a  slide  and  mount  in  balsam.  The  omen  turn 
of  a  rabbit,  cat,  or  dog  may  be  prepared  in  a  similar  manner. 

The  outlines  of  the  endothelial  cells  appear  as  dark  lines  where 
the  silver  has  stained  the  cement-substance.  These  lines  are  often 
tortuous  and  serrated.  The  nuclei  are  not  seen,  unless  they  have 
been  separately  stained  with  carmine  or  some  other  nuclear  dye. 

Openings  called  stomata  occur  on  the  serous  surfaces,  which 
connect  the  cavities  with  underlying  lymphatic  vessels.  The 
stomata  occur  at  the  points  where  several  endothelial  cells  meet. 
The  opening  is  sometimes  surrounded  by  several  small,  granular 
cells,  called  "guard  cells."  Changes  in  the  size  of  these  cells 
modify  the  size  of  the  stomata. 


CONNECTIVE    TISSUES 

Certain  elementary  structures  of  similar  origin  and  mode  of 
development,  and  serving  alike  to  unite  the  various  parts  of  the 
body,  have  been  termed  connective  tissues.  Custom  has  restricted 
the  term,  in  its  everyday  employment,  so  as  to  apply  to  white 
fibrous  tissue,  or,  at  least,  to  tissue  which  always  resembles  this 
more  closely  than  any  other. 

WHITE     FIBROUS     TISSUE 

This,  the  connective  tissue  par  excellence,  is  composed  of  exceed- 
ingly fine  fibrillse  (only  0.6  /*  in  diameter),  which  are  aggregated  in 
irregularly  sized  and  variously  disposed  bundles.  It  forms  long 
and  exceedingly  strong  tendons  connecting  muscle  and  bone;  its 
fibers  interlace,  forming  the  delicate  network  of  areolar  tissue;  it 
forms  thin  sheets  of  protecting  and  connecting  aponeuroses ;  or, 
supporting  vessels,  it  permeates  organs  and  sustains  the  paren- 
chyma of  glands. 

The  fibers  are  held  together  by  means  of  a  transparent  cement, 


CONNECTIVE    TISSUES 


63 


which  may  be  softened  or  dissolved  in  acetic  acid.  They  may 
exist,  as  in  dense  tendons,  without  admixture. 

Cells  are  found  between  the  bundles  of  fibers,  known  as  con- 
nective tissue  corpuscles.  The  older  and  more  dense  the  structure, 
the  less  frequent  are  these  cells;  while  in  young  connective 
tissue,  stained,  the  nuclei  of  the  corpuscles  constitute  a  promi- 
nent feature  of  the  specimen  under  the  microscope. 

Having  obtained  a  piece  of  tendon  from  a  recently  killed  bul- 
lock, tease  a  fragment  on  a  slide  in  a  few  drops  of  water,  Select  a 


FIG.  37.     CONNECTIVE  TISSUE. 

A.  Teased  fibers. 
C.  Fibrillse. 

portion  which  splits  easily  and  separate  the  fibrils    as   much   as 
possible.     Cover,  and  examine   (H). 

Fine,  wavy  fibers  are  seen  composing  the  fasciculi.  If  the 
dissection  has  been  sufficiently  minute,  you  may  succeed  in  demon- 
strating ultimate  fibrillaa.  These  are  best  made  out,  as  at  C  in  Fig. 
37,  where  the  parts  of  a  bundle  have  been  separated  for  some  dis- 
tance, leaving  the  finer  elements  stretching  across  the  interval. 


YELLOW    ELASTIC     TISSUE 


This  tissue  consists  of  coarse,  shining  fibers  (averaging  about  8f- 
in  diameter)  which  frequently  branch  and  anastomose.     They  are 


64 


STUDENTS   HISTOLOGY 


FIG.  38. 


TEASED  YELLOW  ELASTIC  TISSUE  FROM  THE  LIGAMENTUM 
(X  250.) 


FIG.  39.    TRANSVERSE  SECTION  OF  PART  OF  THE  LIGAMENTUM  NUCH^E. 
S.  Sheath  of  the  ligament,  sending  prolongations  within— as  at  T,  T— dividing  the  structure 
into  irregular  bundles  or  fasciculi. 

L.  Lymph-spaces  in  the  connective  tissue. 

A.  Adipose  tissue  in  the  sheath. . 

V.  Blood-vessels  in  transverse  section. 

E,  E.  Primitive  fasciculi  of  yellow  elastic  tissue  fibers. 


ADIPOSE    TISSUE  65 

highly  elastic.     Under  the  microscope  the  fibers  are  colorless,  but 
when  aggregated,  as  in  a  ligament,  the  mass  is  yellow. 

Procure  a  small  piece  of  the  ligamentum  nuchce  of  the  ox,  and 
tease  it  on  the  slide  after  it  has  been  macerated  in  acetic  acid  f OIL 
a  few  moments.     The  acid  softens  the  fibrous  connective  tissue  and 
facilitates  the  teasing  process. 

The  individual  fibers  having  been  isolated,  they  appear  as  in 
Fig.  38.  When  broken,  they  curl  upon  themselves,  like  threads  of 
India  rubber. 

This  tissue  is  variously  disposed  throughout  the  body  where 
great  strength  with  elasticity  becomes  necessary.  The  large 
arteries  are  abundantly  supplied  with  elastic  fiber,  arranged  in 
plates,  in  alternation  with  muscle.  As  a  network,  it  is  mixed  with 
connective  tissue  in  the  skin,  and  in  membranes  generally.  It  con- 
.  tributes  elasticity  to  cartilage  where  the  fibers  form  an  intricate 
network. 

Ligaments  are  composed  largely  of  yellow  elastic  tissue.  Fig. 
39  is  drawn  from  a  portion  of  a  stained  transverse  section  of  part 
of  the  II (j amenta  tsttbflava. 

A  strong  sheath  of  fibrous  tissue  is  thrown  around  the  whole 
ligament,  a  portion  of  which  is  seen  at  S.  This  sheath  sends  pro- 
longations, T,  T,  into  the  structure,  dividing  it  into  irregular 
bundles,  which  support  nutrient  vessels.  The  elastic  fibers  seen  in 
transverse  section,  as  at  E,  E,  are  observed  strongly  bound  together 
with  fibrous  tissue,  which  penetrates  the  smaller  fasciculi,  dividing 
them  into  the  ultimate  fibrillce. 

ADIPOSE     TISSUE 

Adipose  or  fat  tissue  is  a  modification  of  and  development  from 
ordinary  connective  tissue. 

It  originates  in  certain  contiguous  connective  tissue  corpuscles 
becoming  filled  with  minute  fat -globules.  These  ultimately  coa- 
lesce and  form  single  large  globules,  which  bulge  out  the  cell -bodies 
until  they  become  spheroids;  the  nuclei  at  the  same  time  are  dis- 
placed to  the  periphery.  An  aggregation  of  such  cells  forms  a 
lobule  of  adipose  tissue.  The  cells  are  often  so  closely  packed  as 
to  assume  a  polyhedral  form.  From  malnutrition,  this  fat  may  be 
absorbed,  ordinary  connective  tissue  remaining. 

You  will  bear  in  mind  the  fact  that  whenever  fat  exists  in  a 
condition  of  minute  subdivision,  the  particles  always  assume  the 


66 


STUDENTS   HISTOLOGY 


FIG.  40.     CONNECTIVE  TISSUE  CELLS  CONTAINING  FAT — INDICATING  THE  MODE  OF 
FORMATION  OF  ADIPOSE  TISSUE  (X  400). 

A.  Ordinary  elongate  connective  tissue  cells. 

B.  Same  containing  minute  globules  of  fat. 

C.  Coalescence  of  the  fat-globules  and  displacement  of  the  nucleus. 

D.  Still  greater  increase  of  the  fat. 


FIG.  41.     ADIPOSE  TISSUE  FROM  TEASED  HUMAN  OMENTUM.     STAINED  WITH 
HJEMATOXYLIN  (X  400). 

A.  Connective  tissue  framework. 

B.  Just  below  the  letter  is  a  cell  containing  crystallized  fat 


CARTILAGE 


67 


globular  form  ;    and   that  while  adipose  tissue   contains   fat,  fat 
alone  is  not  adipose  tissue. 


CARTILAGE 


Cartilage  consists  of  a  dense  basis  substance,  in  which  cells  or 
corpuscles  are  imbedded.     It  presents  three  forms: 


HYALINE     CARTILAGE 

The  matrix  of  hyaline  cartilage  is  translucent,  dense,  and 
apparently  structureless.  Minute  channels  in  certain  instances 
and  delicate  fibrilla?  in  others  have  been  demonstrated.  The  sur- 
face of  the  cartilage  is  surrounded  by  a  fibrous  envelope,  called 
the  perichondrium . 

The  basis  material  contains  excavations,  generally  spherical, 
called  lacunce.  They  appear  to  be  lined  with  a  membrane,  ,and 


Fig.  42.     SECTION  OF  HYALINE  CARTILAGE  FROM  A  HUMAN  BRONCHUS. 

The  ground-substance  is  apparently  structureless,  and  it  contains  the  lacunae  or  exca- 
vations in  which  one,  two,  three,  or  more  cartilage  cells  appear.  These  cells  show  a  well 
marked  intracellular  network  (X  400). 

contain  one,  two,  three,  and  perhaps  as  many  as  eight  cells — 
the  cartilage -corpuscles.  The  matrix  around  the  lacuna?  is  called 
the  capsule.  It  differs  from  the  rest  of  the  matrix  and  creates  the 
appearance  of  a  membrane  surrounding  the  lacuna?. 

Hyaline  cartilage  is  found  covering  joints  generally,  where  it 


68  STUDENTS   HISTOLOGY 

is  termed  articular  cartilage.     It  is  also  found  in  the  trachea,  the 
bronchi,  the  septum  narium,  etc. 

Fig.  42  shows  a  section  of  hyaline  cartilage  from  one  of  the 
rings  of  a  large  bronchus. 

FIBRO  -  CARTILAGE 

Fibrous  connective  tissue,  predominating  largely  in  the  basis 
substance,  produces  a  structure  of  great  strength— fibro- cartilage. 
The  intervertebral  disks  afford  an  example  of  this  variety,  from  a 


FlG.    43.       FlBRO-CARTILAGE    FROM   AN    INTERVERTEBRAL    PLATE    OR   DlSK. 

The  ground-substance,  unlike  that  of  the  hyaline  varisty,  consists  of  dense  fibrous  tissue 
with  little  calcareous  matter  (X400). 

section  of  which  Fig.  43  has  been  drawn.     The  fibrous  tissue  is  a 
very  prominent  feature  of  the  ground  substance. 


ELASTIC  OR  RETICULAR  CARTILAGE 

As  the  name  implies,  yellow  elastic  tissue  is  an  important  ele- 
ment of  the  ground  -  substance  of  elastic  cartilage.  It  presents 
the  form  of  a  reticulum,  as  shown  in  Fig.  44.  It  is  not  exten- 
sively distributed  in  the  human  being,  although  the  cartilages  of 
the  external  ear,  Eustachian  tube,  epiglottis,  etc.,  are  of  this 
variety. 

Cartilage  should  be  hardened  by  the  chromic  acid  and  alcohol 
process.  '  The  sections  from  which  the  illustrations  have  been 
•drawn  were  cut  without  the  microtome.  They  should  be  cut 


CARTILA  GE—BONE 


FIG.  44.    ELASTIC  CARTILAGE  FROM  EAR  OF  BULLOCK. 
The  ground-substance  consists  largely  of  a  network  of  coarse,  yellow  elastic  tissue  (X400K 


FIG.   45.     PORTION   OF   A    TRANSVERSE    SECTION    FROM   A   DRIED    FEMUR,    SHOWING 
PART  OF  THE  WALL  OF  A  HAVERSIAN  SYSTEM.     (See  pages  70  and  71.) 

A,  A.  Bony  lamellae. 

B,  B.  Lacunae. 

C,  C.  Canaliculi  (X400). 


70 


STUDENTS   HISTOLOGY 


extremely  thin,  but  not  necessarily  large.  We  frequently  succeed 
in  getting  good  fields  from  the  thin  edges  of  sections  which  may 
be  elsewhere  too  thick.  Stain  with  hasmatoxylhi  and  eosin.  The 
differentiation  will  be  excellent.  The  delicate  nutritive  channels 
in  the  matrix  connecting  the  lacunae  may  be  demonstrated  in  the 
cartilage  of  the  sternum  of  the  newt  ;  the  xiphoid  appendix  is 
sufficiently  thin  without  sectioning. 


FIG.  46.     TRANSVERSE    SECTION  OP  PORTION  OP  A  DRIED  LONG  BONE,  SHOWING  THE 

HAVERSIAN  SYSTEMS. 

A,  A,  A.  A  Haversian  system. 

B.  Haversian  canal. 

The  lacunas,  canaliculi,  and  Haversian  canals  all  appear  black  in  the  section,  as  they  are 
filled  with  air  and  the  bony  fragments  resulting  from  grinding  of  the  section  (X60). 


BONE 

Bone  consists  of  an  osseous,  lamellated  matrix,  in  which  occur 
irregularly  -  shaped  cavities — lacunae.  The  latter  are  connected  by 
means  of  exceedingly  fine  channels — canaliculi.  The  lacunaB  con- 
tain the  bone -corpuscles,  the  bodies  of  which  are  projected  into 
the  canaliculi. 


BONE  71 

In  compact  bone,  the  blood-vessels  run  in  a  line  parallel  with 
the  long  axis  of  the  bone,  in  branching  inosculating  channels 
(averaging  about  50  /><<  in  diameter) — the  Haversian  canal*.  The 
lamellae  of  osseous  tissue  are  arranged  concentrically  around  these 


FIG.  47.     SECTION  OF  BONE  SHOWING  SHARPEY'S  FIBERS  PULLEK  OUT  ov  POSITION. 

AFTER  H.  M  TILLER. 

canals.     A  single  Haversian  canal,  and  the  lamella?  surrounding 
and  belonging  to  it,  constitute  a  Haversian  system. 

The  lamellae  beneath  the  periosteum  are  not  arranged  as  above, 
but  parallel  with  the  surface  of  the  bone.  These  plates  are  per- 
forated at  a  right  angle  and  obliquely  by  blood-vessels  from  the 


FIG.  48.     DIAGRAM  OF  A  HAVERSIAN  CANAL. 

A.  Artery. 

B.  Vein. 

C.  Nerve. 

D.  D,  D.   Lymph-channels. 

periosteum,  as  they  pass  on  their  way  to  the  Haversian  canals. 
These  lamellae  are  also  perforated  by  partly  calcined  connective 
tissue — the  perforating  fibers  of  Sharpey.  (Fig.  47.) 

A  Haversian  canal  contains  (Fig.  48)  an  artery,  a  venule, 
lymph -channels,  and  a  nerve -filament.  The  whole  is  supported 
by  connective  tissue  cells  with  delicate  processes.  The  walls 


72  STUDENTS   HISTOLOGY 

of  the  lymph -spaces  are  prolonged  into  the  eanaliculi,  and1 
thus  placed  in  connection  with  the  elements  of  the  surrounding1 
lacunae. 

Each  lacuna  contains  a  bone-corpuscle,  the  protoplasmic  body 
of  which  sends  prolongations  into  the  contiguous  eanaliculi.  In 
the  adult  bone  the  cell  is  shrunken,  and  the  processes  just  .men- 
tioned are»  not  readily  demonstrable. 

The  eanaliculi  of  any  Haversian  system  communicate  with  one 
another,  but  not  with  those  of  different  systems. 

The  concentrically  placed  lamellae  around  the  Haversian  canals 
are.  called  Haversian  lamellce.  The  angular  area  formed  where 
several  Haversian  systems  join  is  filled  out  by  interstitial  lamella., 


FIG.  49.     DIAGRAM  OF  A  BONE  LACUNA. 

A,  A.  Ground-substance  of  the  bone. 

B,  B.  Limiting  membrane  of  the  bone-corpuscle  within  the  lacuna. 

C,  Nucleus  and  nucleolus  of  the  corpuscle. 

D,  D.  Projections  of  the  cell-body  into  the  eanaliculi. 

while  those  lamellae  mentioned  above  as  occurring  just  below  the 
periosteum  are  the  circumferential  or  fundamental  lamellce. 

The  arrangement  of  Haversian  canals  and  their  concentric- 
lamellae  is  confined  to  compact  bone.  Compact  bone  is  formed  on 
the  surface  of  all  bones,  and  makes  up  the  bulk  of  the  shaft  in  long 
bones.  The  other  variety  of  bone,  called  cancellous  or  spongy, 
occurs  extensively  at  the  ends  of  long  bones,  and  in  short  and  flat 
bones.  It  consists  of  lamellae  containing  lacunae  and  eanaliculi, 
lying  between  good  sized  cavities,  which  are  occupied  by  blood- 
vessels and  marrow,  and  which  correspond  to  Haversian  canals. 
Bone  is  to  be  regarded  as  dense  connective  tissue,  arranged  in 
lamellae,  of  which  the  ground-substance  is  impregnated  with  salts 
of  calcium,  chiefly  the  phosphate,  to  which  its  hardness  is  due. 

At  the  same  time,  bone  retains  the  elasticity  and  strength  of 


DEVELOPMENT   OF   BONE  73 

connective  tissue,  which  distinguish  it  from  a  structure  that   has 
merely  been  calcined,  as  may  happen  in  certain  disease  processes. 


PERIOSTEUM 

The  surface  of  bone  is  covered  by  an  envelope  called  periosteum  r 
which  has  two  layers — a  dense,  outer,  fibrous  layer  and  a  looser, 
inner,  vascular  layer.  The  inner  layer  contains  the  cells,  osteoblasts, 
which  form  osseous  tissue,  hence  this  layer  is  called  the  osteogenetic 
layer  of  the  periosteum.  In  operating  on  bone,  surgeons  guard  the 
periosteum  very  carefully,  on  account  of  its  blood-vessels  and  its- 
osteogenetic  elements. 

MARROW 

The  spaces  of  bones  are  everywhere  filled  with  marrow.  The 
largest  of  these  spaces  are  the  medullary  cavities  of  long  bones.  ID 
the  medullary  cavities  the  marrow  is  yellow,  owing  to  the  deposit 
of  fat  in  the  cells.  The  smaller  spaces  of  bone  are  filled  with  red 
marrow.  Red  marrow  contains  marrow -cells,  which  are  similar  to 
connective  tissue  cells,  supported  in  a  very  vascular  connective 
tissue  framework.  The  marrow  cells  are  identical  with  the  osteo- 
blasts  of  the  periosteum  and  with  bone-corpuscles.  Immense  cells, 
giant  cells,  containing  many  nuclei,  also  occur  in  red  marrow.  On 
account  of  their  function  of  absorbing  superfluous  bone,  they  are 
called  osteoclasts  (Fig.  50).  Red  marrow  also  contains  nucleated 
cells,  tinged  with  hemoglobin,  that  are  connected  with  the  forma- 
tion of  red  blood -corpuscles,  which  probably  takes  place  exten- 
sively in  the  red  marrow. 

DEVELOPMENT     OF     BONE 

The  majority  of  the  bones  of  the  body  are  first  formed  in  the 
embryo  as  hyaline  cartilage,  which  is  subsequently  replaced  by  true 
bone — endochondral  ossification . 

'The  bones  of  the  face  and  of  the  vault  of  the  cranium  and  a 
portion  of  the  lower  jaw  are  the  principal  exceptions — intramem- 
branous  ossification.  In  the  latter  case,  the  basis  of  the  forming 
bone  is  an  embryonic  fibrous  tissue,  and  this  form  of  ossification 
differs  from  the  endochondral  in  not  being  carried  on  in  a  carti- 
laginous basis,  which  is,  however,  a  temporary  structure. 


74  STUDENTS   HISTOLOGY 

(a)  In  the  case  of  endochondral  bone,  the  commencement  of 
ossification  is  indicated  by  the  enlargement  of  the  cartilage -cells 
and  their  arrangement  into  vertical  rows.  This  takes  place  at  a 
point  called  the  center  of  ossification.  (?>)  The- matrix  between  them 
becomes  calcified,  (c)  From  the  surface  of  the  bone,  which  is 
covered  by  a  membrane  corresponding  to  the  periosteum,  processes 
extend  into  the  cartilage,  (d)  The  cartilage  is  absorbed  to  make 
room  for  these  processes  through  the  agency  of  the  osteoclasts 
(see  Fig.  50).  (e)  The  absorption  proceeds  until  it  includes  the 
region  of  calcified  cartilage.  (/)  The  osteoblasts,  which  have 
accompanied  the  periostea!  ingrowth,  arrange  themselves  .on  the 
surface  of  the  spaces  resulting  from  absorption  of  the  cartilage,  and 
form  layers  of  bone,  (g)  At  the  same  time  the  osteoblasts  of  the 
osteogenetic  layer  of  the  periosteum  form  layers  of  bone  beneath 
the  periosteum — periosteal  ossification. 

The  first  bone  formed  is  soft  and  spongy.  It  will  be  observed 
that  as  ossification  proceeds  the  whole  of  the  cartilage  will  be 
absorbed,  except  that  at  the  epiphyses.  In  the  course  of  the 
growth  of  the  individual,  the  network  and  spaces  of  the  origi- 
nal spongy  bone  undergo  considerable  rearrangement.  Haver- 


FIG.  50.  CELLS  FROM  RED  MARROW  OF  RABBIT  (PRUDDEX). 

A.  Marrow  cells  proper. 

B.  Giant  cells. 

sian  systems  result  from  deposition  of  successive  layers  of 
lamellae  around  the  spaces  of  spongy  bone,  from  without  inward, 
leaving  a  channel  at  the  center,  which  is  the  Haversian  canal. 
The  medullary  cavity  is  produced  by  the  absorption  of  the  central 
part  of  the  bone,  while  new  layers  continue  to  form  under  the 
periosteum. 


SECTIONS    OF   BONE 


75 


PIG.  51.     DEVELOPING  BONE,  FROM  THE  PIG  (PRUDDEN). 

Fig.  46  lias  been  drawn  from  a  section  of  dry  bone  which  has 
been  sawn  as  thin  as  possible,  and  afterward  rubbed  down  on  a 
hone  with  water.  It  is  a  tedious  process,  and  shows  little  but  the 
osseous  matrix.  Bone  should  be  decalcified  for  microscopical 
work,  and  it  may  then  be  readily  cut  in  thin  sections  with  a  razor. 
The  process*  is  as  follows: 

To  100  c.c.  of  the  dilute  chromic  acid  solution  add  3  c.c.  of 
0.  P.  nitric  acid.  The  bone,  previously  divided  into  slices  not 
over  one -half  centimeter  in  thickness,  is  then  placed  in  the  fluid, 
and  should  be  completely  decalcified  in  a  week  or  ten  days. 
Examine  the  pieces  after  twenty -four  hours  by  puncturing  with  a 
needle.  Should  the  action  proceed  too  slowly,  add  a  few  drops 
more  of  the  nitric  acid  from  time  to  time.  The  bone  eventually 
takes  on  a  green  color.  After  complete  decalcification,  wash  the 
pieces  for  twenty-four  hours  in  clean  water,  and  preserve  them, 
until  required,  in  80  per  cent,  alcohol.  Small  pieces  of  young 
bone  may  be  decalcified  in  a  saturated  aqueous  solution  of  picric 


76  STUDENTS   HISTOLOGY 

acid.      The  process  is  slow,  but  it  leaves  the  tissue  in  excellent 
condition . 

Sections  cut  in  the  usual  way  may  be  stained  with  carmine  and 
picric  acid,  and  examined  in  a  drop  of  glycerin.  They  should  not, 
after  the  staining,  be  placed  in  the  oil  of  cloves,  as  they  would  curl 
and  become  hard.  Transfer  them  to  equal  parts  of  glycerin  and 
water,  from  which  they  are  to  be  carried  to  the  slide.  Add  a  drop 
more  of  the  dilute  glycerin  if  necessary  and  put  on  the  cover -glass, 
carefully  avoiding  air -bubbles.  If  you  desire  to  make  a  perma- 
nent mounting,  the  edge  of  the  cover  must  be  cemented  to  the 
slide. 

Thoroughly  wipe  the  slide  around  the  cover  with  moistened 
paper,  until  every  trace  of  glycerin  is  removed.  Then  with  a  sable 
brush,  paint  a  ring  of  zinc  cement  (vide  formulae)  around  the 
slide  just  touching  the  edge  of  the  cover -glass.  Repeat  the 
cementing  in  twenty -four  hours.  A  turn-table  will  be  a  useful 
aid  in  this  work. 

SPECIAL    CONNECTIVE    TISSUES 

Connective  Tissue  of  the  Lymphatic  System. — The  matrix  of 
lymphoid  or  adenoid  tissue  consists  of  a  network  of  fibers  and 
cells,  which  support  the  lymph -corpuscles.  It  is  distributed  exten- 
sively in  organs,  and  where  it  appears  in  stained  sections,  the 
lymphoid  cells  are  so  numerous  as  to  obscure  the  reticulum  almost 
entirely.  The  structure  will  be  minutely  described  in  connection 
with  the  lymphatic  system. 

Embryonic    Connective   Tissue  presents  a  homogenous,  mucoid 
matrix  containing  branched  cells.     It  is  not  found  normally  in  the 
adult.     The  jelly  of  Wharton  of  the  umbilical  cord  is  mucoid  tissue. 
i 

MUSCULAR    TISSUE 

This  tissue  is  found  in  three  varieties:  1.  Non-striated,  smooth 
or  in  voluntary.  2.  Striated,  skeletal,  or  voluntary.  3.  Cardiac. 

NON- STRIATED    MUSCLE 

The  histological  element  of  non- striated  muscle  is  a  spindle- 
shaped  cell  from  45-225  p  long  and  4-7  p  broad.  The  cell  body 
presents  longitudinal  striae,  and  contains  an  ovoid  nucleus.  The 
nucleus  contains  a  reticulum  which  is  probably  in  connection  with 


NON- STRIATED    MUSCLE 


77 


the  fibrillae,  which  produce  the  longitudinal  striation  of  the  body. 
The  cells  are  not  infrequently  bifid  at  one  or  both  extremities. 
A  transparent  cement  substance  serves  to  unite  these  cells  in  form- 
ing, with  connecting  tissue,  broad  membranous  plates,  bundles, 


A| 


FIG,  52.     NON-STRIATED  MUSCLE.     (SCHAFER.) 

A.  Complete  cell. 

B.  Broken  cell. 

plexuses,  etc.     It  serves  to  afford  contractility,  especially  to  the 
organs  of  vegetative  life. 

Kill  a  good -sized  frog  by  decapitation,  and  open  the  abdomen 
on  the  median  line.  Fill  the  bladder  with  air,  after  the  introduc- 
tion of  a  blow -pipe  into  the  vent.  Remove  the  inflated  bladder 


78 


STUDENTS   HISTOLOGY 


with  a  single  cut  with  the  curved  scissors,  and  place  it  in  a  saucer 
of  water.  Proceed  to  brush  it,  under  the  water,  with  two  camel's- 
hair  pencils,  so  as  to  remove  all  of  the  cells  from  the  inner  surface. 
It  will  bear  vigorous  rubbing  with  one  of  the  brushes,  holding  it 
at  the  same  time  with  the  other.  Transfer  to  alcohol  for  ten 
minutes,  and  afterward  stain  with  hsematoxylin  and  eosin.  While 
in  the  oil,  cut  the  tissue  into  small  pieces,  and  mount  flat  in 
balsam.  Examine  with  L  and  H. 

Observe  the  bands  of  involuntary  muscle  crossing  in  various 
directions.  You  will  distinguish  between  the  muscle  and  the  con- 
nective tissue  cells  by  their  nuclei. 


STRIATED    MUSCULAR    TISSUE 


A  skeletal  or  striated  muscle  consists  of  cylindrical  fibers,  vary- 
ing from  10 p  to  100  p-  in  diameter  and  5  to  12  cm.  long.  These 
primitive  fibers  are  supported  by  a  delicate,  transparent  sheath— 
the  sarcolemma.  They  are  aggregated,  forming  primitive  fasciculi, 
which  are  again  united  to  form  the  larger  bundles  of  a  complete 


FIG.  53.     PART  OF  A  MUSCLE  FIBER.     (RANVIKR.) 

A.  Dark  disk. 

B.  Membrane  of  Krause. 
•0.  Light  disk. 

N.  Muscle  nucleus. 

muscle.  The  connective  tissue  uniting  the  primitive  fibers  is 
termed  endomysium;  while  that  uniting  the  primitive  bundles  is 
the  perimysium. 

The  primitive  muscular  fibers  exhibit  marked  cross  striations 
with  faint  longitudinal  markings,  the  former  being  produced  by 
alternate  dark  and  light  spaces. 


STRIATED    MUSCLE 


79 


Under  very  high  magnification  each  light  band  appears  to  be 
crossed  by  a  dark  line,  called  the  intermediate  disk  or  membrane  of 
Kranse.  The  dark  band  consists  of  rows  of  spindle-shaped  bodies. 


FIG.  54.     STRIATED  MUSCULAR  FIBERS  FROM  THE  TONGUE,  TEASED  AND  STAINED 

WITH    H^EMATOXYLIN    (X  400). 

A.  A  fiber,  with  the  muscle  substance  wanting,  from  stretching  during  the  teasing,  the  sar- 
colemma  alone  remaining. 

B.  Partly  separated  disk  of  Bowman. 

C.  Ultimate  fibrillae. 

D.  A  blood-capillary. 


Those  of  the  different  dark  bands  are  placed  end  to  end,  forming- 
continuous  elements.  They  constitute  the  contractile  fibrillce. 
The  light  bands  correspond  to  the  attenuated  ends  of  the  spindle- 
shaped  bodies.  Little  knobs  on  the  ends  of  the  spindles  make 
the  dark  line  called  the  intermediate  disk.  The  fibrilla?  are 
held  in  bundles  by  a  pale  sarcoplasm.  In  transverse  sec- 
tions of  muscle  these  bundles  show  as  polygonal  areas  —  Colin- 
lie  im1  s  fields. 

Macerate  human  muscle,  preferably  that  from  the  tongue,  in 
dilute  chromic  acid  for  twenty  -four  hours,  wash,  tease  in  water, 


.80 


STUDENTS  HISTOLOGY 


-cover,    and   focus   with    H.       Fig.    54    was    drawn   from    such   a 
preparation. 

The  sarcolemma  is  best  seen  where  the  contractile  substance 
las  been  broken.  The  muscle  nuclei  are  seen  at  various  points 
beneath  the  sarcolemma.  Portions  of  a  fiber  have  been  split  off 
transversely  in  places,  indicating  the  disk  of  Bowman.  The 
fibrillae  are  indicated  where  the  fiber  has  been  split  longitudinally 
during  the  teasing.  The  capillaries  are  arranged  in  a  direction 
parallel  to  the  fibers,  with  frequent  transverse  connections. 


CARDIAC     MUSCULAR    FIBER 

It  presents  the  following  characteristics: 

1.  The  fibers  are  smaller  than  those  of  ordinary  skeletal  muscle. 

2.  They  are  striated  both  transversely  and  longitudinally. 

3.  They  branch,  forming  frequent  inosculations. 


FIG.  55.     TEASED  CARDIAC  MUSCULAR  FIBERS. 
Stained  with  haematoxylin,  X  400  and  reduced. 

4.  They  are  divided  by  distinct  transverse  lines  into  short  cells. 

5.  Their  nuclei  are  situated  within  the  fiber. 

6.  They  present  no  distinct  sarcolemma. 

Notice  the  groups  of  yellowish  brown  pigment -granules  within 
the  muscle-cells  close  to  the  nuclei.  Fig.  55  has  been  drawn  from 
fresh  cardiac  muscle,  teased  in  normal  salt  solution  and  tinted 
with  eosin. 


NERVOUS    TISSUES— BLOOD 


81 


NERVOUS    TISSUES 

Following  the  order  given  in  the  classification  of  tissues,  the 
nervous  tissues  should  be  studied  at  this  point.  But  in  laboratory 
work  it  will  be  found  more  satisfactory  to  consider  them  in  con- 
nection with  the  histology  of  the  central  nervous  system  (see 
page  216). 

BLOOD 

The  human  red  blood -corpuscle  is  a  flattened,  bi- concave  disk, 
circular  in  outline,  and  from  7  p  to  8  M  (Woro  inch)  in  diameter.  It 


FIG.  50.     CORPUSCULAR  ELEMENTS  OF  HUMAN  BLOOD  (X  400). 

A.  Colored  corpuscles  adhering  by  their  sides — rouleaux. 

B.  The  same  crenated. 

C.  The  same  shrunken. 

I).  The  same  having  absorbed  water. 

E.  The  same  still  more  swollen. 

F.  The  same  with  the  plane  C  D,  Fig.  57,  in  focus. 

G.  The  same  with  the  plane  A  B,  Fig.  57  in  focus. 
H.   Colorless  corpuscles. 

presents  a  mass  of  protoplasm  destitute,  as  far  as  the  microscope 
shows,  of  nuclei,  cell -wall,  or  any  structure  whatsoever. 

Certain  changes  in  form  result,  after  removal  from  the  circula- 
tion, viz.:      1.  They  may  adhere  by  their  broad  surfaces  forming 


82  STUDENTS   HISTOLOGY 

columns.  2.  From  shrinkage  they  may  become  crenated.  3.  Still 
further  shrinkage  produces  the  chestnut -burr  appearance.  4. 
From  absorption  of  water  they  may  swell  irregularly,  obliterating 
the  concavity  of  one  side.  5.  From  continuous  absorption  they 
swell,  forming  spheres  which  are  finally  dissolved. 

Wind  a  twisted  handkerchief  tightly  around  the  left  ring-finger, 


FIG.  57.     DIAGRAM  OF  A  COLORED  BLOOD-CORPUSCLE,  SIDE  VIEW,  SHOWING  THE 
Bi -CONCAVITY.     (The  thickness  is  exaggerated.) 

A,  B.  Upper  plane,  which,  in  focus,  gives  the  appearance  shown  at  G,  Fig.  56. 
C,  D.  Plane  giving  the  appearance  shown  at  F,  Fig.  56. 

prick  the  end  with  a  clean  needle,  and  squeeze  a  minute  drop  of 
blood  on  a  slide,  add  a  drop  of  salt  solution,  cover,  and  focus 
with  H. 

Observe:  1.  That  considerable  variation  in  size  of  the  red 
blood -corpuscles  exists.  2.  The  color— a  delicate  straw  tint. 
3.  That  the  concave  centers  of  the  corpuscles  which  lie  flat  can  be 
made  to  appear  alternately  dark  and  light  according  to  the  focal 
adjustment.  4.  That  the  concavity  is  also  demonstrated  as  the 
corpuscles  are  turned  over  by  the  thermal  currents.* 

BLOOD -PLATES 

Minute  corpuscular  elements  in  the  blood,  about  one-fourth  the 
size  of  the  red  disks,  exist  in  the  proportion  of  about  one  of  the 
former  to  twenty  of  the  latter.  They  are  colorless  ovoid  disks, 
and  are  regarded  by  Osier  as  an  essential  factor  in  the  coagulation 
of  the  blood. 

Prick  the  thoroughly  clean  finger  with  a  needle.  Over  the 
puncture  place  a  drop  of  solution  of  osmic  acid  (one  per  cent.),  and 
squeeze  out  a  minute  drop  of  blood,  so  that,  as  it  flows,  it  is  covered 
by  the  acid  solution.  This  fixes  the  anatomical  elements,  provid- 
ing against  further  change.  The  blood,  as  soon  as  drawn,  must, 
with  the  acid,  be  immediately  transferred  to  a  slide  and  covered. 

"The  student  is  at  this  time  advised  to  study  the  corpuscular  elements  of  the  blood  of  such 
animals  as  he  may  be  able  to  command.  The  red  corpuscles  of  mammals  (excepting  the 
camelidae)  do  not  vary  in  appearance  from  those  of  man,  excepting  in  size.  Those  of  birds, 
fishes,  and  reptiles  are  elliptical,  with  oval  nuclei.  Corpuscles  of  the  blood  of  invertebrates  are 
not  colored. 


WHITE   BLOOD- CORPUSCLES  83 

To  provide  against  evaporation,  run  a  drop  of  sweet  oil  around  the 
edge  of  the  cover. 

The  blood -plates  may  be  found,  after  careful  search,  bearing 
the  relation  to  the  red  corpuscles  seen  in  Fig.  58. 

WHITE  OR  COLORLESS  BLOOD -CORPUSCLES 

The  white  blood -corpuscles  are  also  called  leucocytes.  In  fresh 
preparations  they  are  seen  to  be  perfectly  colorless,  nearly  spherical 
cells,  often  slightly  granular.  The  nucleus  is  distinguished  with 
difficulty  unless  reagents  are  used.  The  leucocytes  are  not  all  of 
the  same  size.  The  larger  ones  are  the  more  numerous.  If  they 
are  watched  carefully,  the  larger  ones  may  be  observed  to  change 


FIG.  58.     HUMAN  BLOOD  PRESERVED  WITH  OSMIC  ACID. 

A.  Colored  corpuscles. 

B.  Colorless  corpuscle. 

C.  C,  C.  Groups  of  plaques.   (X  400  and  reduced.) 

their  shapes  slowly.  This  movement  is  a  property  belonging 
to  their  protoplasm  called  amoeboid  movement.*  Portions  of 
the  protoplasm  are  slowly  extended  outwards,  making  projections 
called  pseudopodia,  which  may  be 'drawn  in  again.  By  means 
of  this  movement  the  leucocytes  can  travel  slowly  from  one  part 
of  the  field  to  another.  They  are  more  active  when  the  slide  is 
warmed  slightly. 

*The  Amoeba  is  an  exti-emely  simple  unicellular  animal  (Protozoon),  which  is  found  in 
the  water  of  ponds.  It  is  usually  much  larger  than  the  white  blood -corpuscle,  and  its  move- 
ment is  ordinarily  very  active  and  easily  seen.  The  student  should  examine  specimens  of 
water  and  watch  the  movement  of  the  Amoeba. 


$4  STUDENTS   HISTOLOGY 

The  leucocytes,  especially  the  larger  ones,  are  of  great  impor- 
tance in  pathology  in  connection  with  inflammation  and  the  forma- 
tion of  pus.  The  large  leucocytes  furnish  the  great  majority  of 
the  cells  in  ordinary  pus.  The  smaller  leucocytes  are  about  the 
size  of  the  red  corpuscles;  the  larger  ones  are  about  13  ^  in  diam- 
eter. The  leucocytes  are  very  much  less  numerous  than  the  red 
•corpuscles.  The  ratio  to  the  red  corpuscles  varies  from  1  to  500 
to  1  to  1,000.  The  leucocytes  become  more  numerous  a  few  hours 
after  eating. 

In  order  to  study  the  leucocytes  more  carefully,  they  should  be  examined 
in  dried  and  stained  preparations,  with  an  oil- immersion  lens  if  possible. 
.Square  cover-glasses  are  used,  which  need  to  be  clean  and  perfectly  free 
from  dust.  They  should  be  handled  with  forceps.  Having  cleaned  and  dried 
the  skin  of  the  finger,  puncture  it  quickly  with  a  clean,  sharp  needle,  using  no 
pressure.  A  drop  of  blood  should  be  allowed  to  issue.  Wipe  away  the  first 
•drop,  and  use  the  next,  which  should  be  no  larger  than  a  pin's  head.  Apply 
the  surface  of  one  cover-glass  to  the  summit  of  the  drop.  Let  this  cover- 
glass  fall  on  the  other  at  the  angle  shown  in  Fig.  59.  The  blood  is  spread 
between  the  cover-glasses  in  a  thin  film.  Quickly  draw  them  apart,  without 
lifting.  The  film  of  blood  dries  immediately.  The  object  is  to  spread  the 
t>lood  on  the  cover-glass  in  a  thin  film  within  a  few  seconds  after  it  leaves 
the  capillaries,  before  coagulation  or  changes  in  the  shapes  of  the  cells  can 
occur. 

To  fix  the  preparations  they  should  be  placed  in  a  mixture  of  alcohol  and 
ether -(equal  parts)  for  half  an  hour;  or  they  may  be  subjected  to  dry  heat 
(110°  C.)  preferably  for  half  an  hour  or  even  longer. 

There  are  many  methods  of  staining.  Much  can  be  done  with  the  ordi- 
nary hsematoxylin  and  eosin  stain.  Very  beautiful  results  can  be  obtained 


FIG.  59.     MANNER  OF  PLACING  COVER-GLASSES.   (CABOT.) 


"with  combinations  of  aniline  dyes;  for  instance,  eosin  and  methylene  blue:  one- 
half  per  cent,  solution  of  eosin  in  sixty  per  cent,  alcohol  three  minutes ;  wash ; 
dry,  by  pressing  between  two  pieces  of  filter  paper;  strong  watery  solution 
of  methylene  blue,  one  minute;  wash;  dry;  balsam. 

The  very  large  nucleated  red  blood-corpuscles  of  the  frog  and  newt  should 
Ibe  stained  in  this  manner. 


WHITE   BLOOD-CORPUSCLES  85- 

To  study  the  leucocytes  of  human  blood  after  fixation,  preferably  with  heat, 
use  the  Ehrlich  tricolor  stain  (p.  32)  for  five  minutes  ;  wash,  dry,  mount 
in  balsam.  The  red  corpuscles  are  stained  orange -yellow  to  brown.  The 
nuclei  of  the  leucocytes  are  stained  green. 

The  Ehrlich  method  of  staining  shows  us  that  the  leucocytes, 
are  of  several  kinds.  Some  have  large,  round  nuclei;  others- 


A  B 

FIG.  GO.     VARIETIES  OF  LEUCOCYTES. 

A.  Small  Lymphocytes. 

B.  Large  Lymphocytes. 

C.  Polymorpho-nuclear  Neutrophiles. 

D.  Eosinophile. 

have  nuclei  that  are  distorted  or  that  appear  to  be  in  several 
parts.  Some  have  stained  granules  in  their  protoplasm;  others 
have  no  granules.  The  nature  of  the  granules  and  their  affinities 
for  the  aniline  dyes  have  been  described  in  the  chapter  on  staining. 
The  granules  in  the  leucocytes  of  man  are  of  two  sorts:  (a)  Neu- 
trophile  granules,  very  small  and  numerous  dust -like  granules  of 
a  reddish  brown  color;  the  leucocytes  containing  them  look  as 
though  they  had  been  sprinkled  with  red  pepper,  (b)  Eosinophila 
granules — good  sized,  round,  shining  granules,  not  so  numerous 
in  the  cells  as  the  last. 

These  characters  enable  us  to  classify  leucocytes  as  follows: 

1.  Small  lymphocytes,  which  have  a  large,  round  nucleus  and  a 
thin  band  of  protoplasm  with  no  granules.     They  are  the  same  as 
the  lymphoid  cells  of  the  lymph- nodes  and  lymph  from  which  they 
originate.     They  make  twenty  per  cent,  to  thirty  per  cent,  of  all 
leucocytes. 

2.  Large  lymphocytes,  or  large  mononuclear  leucocytes.     They 
have  a  round  or  indented  nucleus,  and  a  considerable  amount  of 
protoplasm,  without  granules.       Those  with   indented  nuclei  are 
often  known  as   transitional  forms.      The  large  lymphocytes  are 
not  numerous — four  to  eight  per  cent. 


86 


STUDENTS   HISTOLOGY 


3.  Polymorphonuclear  neutrophiles   (often   called   polynuclear) . 
The  nuclei  are  much  indented,  or  even  seem  to  exist  as  several 
different  parts.     They  contain  immense  numbers  of  fine  neutro- 
phile  granules.     They  constitute  the  majority  of  leucocytes — sixty- 
two  to  seventy  per  cent. 

4.  Eosinophiles,  which  have  polymorphous  nuclei  and  eosino- 


B 


\7 


FIG.  61.    MIXING  PIPETTES.    (CABOT.) 

A.  For  red  blood-corpuscles.    It  is  the  one  referred  to  in  the  text. 

B.  For  white  blood-corpuscles,  where  the  dilution  is  not  so  great.    Weak  acetic  acid  is  used 
as  a  diluting  fluid,  which  decolorizes  the  red  corpuscles  so  that  the  white  corpuscles  alone  are 


phile  granules.  They  are  of  great  importance  in  some  of  the 
diseases  of  the  blood.  The  proportion  of  eosinophiles  is  from  one- 
half  to  four  per  cent.* 


*The  percentages  given  are  quoted  from  Cabot:  Clinical  Examination  of  the  Blood,  to  which 
the  student  is  referred  for  further  information  on  this  subject. 


ENUMERATION  OF  BLOOD-CORPUSCLES 


87 


In  disease  the  percentages  above  given  are  subject  to  much 
variation. 

Cells  that  contain  basophile  granules  are  occasionally  seen  in 
normal  human  blood,  as  well  as  in  disease.  Their  significance  js 
not  understood.  They  are  not  demonstrated  by  the  Ehrlich  tri- 
color stain.  They  are  easily  found  in  the  blood  of  the  Amphibia, 
by  staining  with  basic  dyes. 

There  is  some  reason  for  believing  that  the  lymphocyte  is  the 
youngest  form  of  leucocyte,  and  that  the  other  varieties  are 
developed  from  it  in  succession  while  circulating  in  the  blood- 
channels. 

ENUMERATION     OF     BLOOD  -  CORPUSCLES 

The  number  of  blood -corpuscles  in  a  cubic  millimeter  of  blood 
may  be  determined  quite  accurately  by  means  of  the  haemocyto- 
meter.  To  lessen  the  labor  of  counting,  the  blood  is  diluted  with 
normal  salt  solution  or  Toison's  fluid.* 

The  blood  is  drawn  into  the  pipette,  Fig.  61  A,  to  the  point  marked  0.5,  or  to 
1.0,  and  then  the  fluid  is  drawn  in  till  the  bulb  is  filled  to  101.0.  With  the 
finger  on  the  end  of  the  pipette  it  is  shaken  to  mix  the  blood  with  the  solution. 
Discarding  the  first  drop,  a  small  quantity  is  placed  in  the  center  of  the  small 


FIG.  62.     PLATE  AND  RULED  DISK  OF  THE  H^MOCYTOMETEK. 


disk  in  the  middle  of  the  slide,  Fig.  62.     The  cover-glass,  which  goes  with  the 
instrument,  is  placed. over  the  drop.     Air  bubbles  are  to  be  avoided,  and  no  dust 

*Toison's  fluid — 

Methyl  violet.    5B 025  grams. 

Sodium  chloride 1. 

Sodium  sulphate 8. 

Glycerin 30  c.c. 

Water 160  c.c. 

The  leucocytes  are  stained  faintly  purple.    The  red  blood-cor-puscles  retain  their  normal  color 
and  form. 


88 


STUDENTS   HISTOLOGY 


particles  or  fluid  should  separate  the  cover-glass  from  the  surface  of  the  square 
of  glass  surrounding  the  disk. 

The  disk  is  depressed  -n>  mm.  below  the  upper  surface  of  the  square. 
It  is  also  ruled  into  400  squares  -^  mm.  on  each  side.  When  the  blood- 
corpuscles  fall  to  the  surface  of  the  di^k,  as  they  do  after  a  few  minutes,  the 
number  counted  in  one  square  represents  those  present  in  Tcfoo"  cu.mm.  of 
the  diluted  blood.  UVX  a^X  TO-)  Every  fifth  square  is  crossed  by  a  second 
ruled  line,  which  encloses  the  small  squares  into  groups  of  sixteens  and  assists 
in  counting.  Using  the  high-power,  tne  corpuscles  in  a  given  number  of 
squares  in  various  parts  of  the  plate  are  counted.  In  counting,  discard  the 
corpuscles  that  touch  the  lines  on  two  sides  (above  and  at  the  right),  and 


FIG.  63.    APPEARANCE  OF  FIELD  OF  HJEMOCYTOMETER 
UNDER  HIGH-POWER.     (FREEBORN.) 

count  those  that  touch  the  other  two  (below  and  at  the  left);  the  average  for 
one  small  square  is  thus  taken.  It  is  best  to  wipe  away  the  first  drop  after 
a  number  of  squares  have  been  counted,  replacing  it  with  another,  after 
thoroughly  shaking  the  pipette.  In  all,  count  the  number  in  about  four 
hundred  small  squares.  Multiply  the  average  number  for  one  square  by  4,000 
and  by  the  dilution  (100  or  200),  and  the  number  of  red  (or  white)  corpuscles 
in  a  cubic  millimeter  of  blood  is  obtained. 


The  number  of  red  blood -corpuscles  in  a  cu.mm.  of  human 
blood  is  5,000,000,  or  somewhat  more,  for  men,  and  about  half  a 
million  less  for  women.  The  normal  number  of  white  corpuscles 
is  from  5,000  to  10,000  in  a  cu.mm. 


HEMOGLOBIN 


HAEMOGLOBIN 


The  substance  that  gives  to  the  red  blood -corpuscles  their  char- 
acteristic color  is  haemoglobin,  which  has  the  important  function^ 
of  being  the  oxygen -carrier  of  the  corpuscle.     The  haemoglobin  of 
most  mammals  crystallizes  in  the  form  of  rhombic  prisms  of  a  red 
color.     That  of  the  rat  crystallizes  quite  readily. 


FIG.  64.     CRYSTALS  OP  HEMOGLOBIN.     (RANVIER.) 

A,  B.   Of  man. 

C.  Of  cat. 

D.  Of  guinea  pig. 

E.  Of  hamster. 

F.  Of  squirrel. 


Haematoidin  and  haemosiderin  are  substances  derived  from 
haemoglobin  often  found  in  pathological  tissues,  as  after  haemor- 
rhages. Haemosiderin  contains  iron,  and  occurs  as  yellow  or  brown 
granules.  Haematoidin,  which  is  the  same  as  bilirubin,  contains 
no  iron,  and  occurs  as  granules  or  rhombic  plates  of  a  yellow  to 
brown  color. 


90  STUDENTS   HISTOLOGY 


H^EMIN     CRYSTALS 

Let  a  drop  of  blood  dry  on  a  slide.  Add  a  few  drops  of  glacial  acetic  acid, 
and  heat  over  a  flame  until  bubbles  appear.  Dry  and  mount  in  balsam.  Dark 
brown  rhombic  prisms  will  be  seen,  which  are  crystals  of  hsemin,  or  the  crystals 
of  Teichmann.  They  are  proof  of  the  presence  of  blood,  but  do  not  indicate 
its  source.  They  may  be  of  importance  in  medico -legal  cases. 


FIBRIN 

The  delicate  network  of  straight  fibrin  filaments  is  easily  demonstrated  by 
the  method  recommended  by  Gage.  A  large  drop  of  blood  is  placed  on  a  slide, 
and  is  covered  with  a  cover-glass.  The  slide  is  laid  on  a  piece  of  wet  blotting 
paper,  and  covered  with  a  saucer  to  prevent  evaporation.  After  half  an  hour 
coagulation  will  have  occurred.  Draw  a  drop  of  water  around  the  edge  of  the 
coVer-glass,  and  float  it  carefully  from  the  slide,  endeavoring  to  keep  the 
coagulum  of  fibrin  on  the  cover-glass.  Wash  carefully  in  water,  stain  in 
hsematoxylin  and  eosin;  dry;  mount  in  balsam.  (Gage  recommends  mounting 
•without  balsam  over  a  hard-rubber  cell.) 

EFFECT     OF     REAGENTS 

Reagents  produce  characteristic  changes  in  the  blood-corpuscles. 
A  strong  saline  solution  leads  to  the  formation  of  projections  on 


FIG.  65.     BLOOD-CORPUSCLES  OF  FROG.     (RANVIER.) 

the  red  corpuscles,  known  as  crenation;  if  sufficiently  concentrated, 
the  corpuscle  becomes  a  shrunken,  shapeless  mass.  Water  causes 
the  red  corpuscles  to  swell  ;  the  haBmoglobin  is  finally  dissolved 
out,  leaving  the  colorless,  barely  visible  outline  of  the  stroma  called 


DEVELOPMENT   OF   THE    BED    BLOOD-CORPUSCLES  91 

the  "ghost."  After  the  addition  of  water  the  white  corpuscles 
become'  spherical ;  their  granules  display  the  dancing  "  Brownian 
motion; "  they  swell,  and  finally  burst.  Weak  acetic  acid  decolorizes 
the  red  corpuscles,  and  clears  the  granules  of  the  white  corpuscles 
so  that  their  nuclei  become  visible.  Weak  solutions  of  tannic  acid 
coagulate  the  coloring  matter  of  the  red  corpuscles,  which  escapes 
from  the  cell,  clinging  as  a  minute  particle  to  one  edge. 

DEVELOPMENT     OF    THE     RED     BLOOD -CORPUSCLES 

The  red  blood -corpuscles  of  the  mammalian  embryo  possess 
nuclei,  and  in  this  respect  resemble  those  of  birds,  reptiles,  amphib- 
ians, and  fishes.* 

The  nucleated  red  corpuscles  of  the  mammalian  embryo  and  of 
the  young  forms  of  the  lower  vertebrates  multiply  by  karyokinesis. 
At  birth,  however,  in  mammals  the  nucleated  corpuscles  are  found 
to  have  been  replaced  by  the  ordinary,  non- nucleated,  discoidal 
forms.  The  origin  of  the  non -nucleated  corpuscles  and  the  man- 
ner of  their  renewal  throughout  life  are  uncertain.  It  has  been- 
suggested  that  they  are  developed  from  leucocytes  and  also  from 
the  blood -plates,  but  both  of  these  theories  lack  confirmation.  It 
seems  probable  that  the  nucleated  cells  colored  with  haemoglobin, 
found  in  the  red  marrow  of  the  bones,  are  the  most  important 
source  of  the  red  corpuscles.  According  to  Ho  well,  the  nucleated 
red  corpuscles  of  the  marrow  lose  their  nuclei  by  extruding 
them. 


*The  red  blood-corpuscles  of  the  order  of  fishes  known  as  Cyclostomi,  of  which  the  lamprey 
is  a  member,  are  circular,  nucleated  disks.     Amphioxus  has  no  red  blood-corpuscles. 


PART   THIRD 
ORGANS 

THE    SKIN 

The  skin  consists  of  (1)  the  epidermis  (or  scarf  skin),  which 
everywhere  covers  and  protects  (2)  the  derma  (corium  or  true 
skin ) . 

The  epidermis  varies  greatly  in  thickness  in  different  locations; 
and  in  the  thicker  portions  several  layers  may  be  differentiated. 
It  is  composed  entirely  of  cells,  while  the  derma  is  fibrous. 

1.  Stratum  Corneum,  )  T 

2.  Stratum  Lucidum,  j  Horny  Lftyer-  i    & 


r^  li  \  3.  Stratum  Granulosum,  1  AT  ,   .  ,  .       T 

'M      4.  Stratum  of  Prickle  Cells,  Malpighian  Layer  or 

t       1  5.  Stratum  of  Columnar  Cells.  }       Eete  Mucosnm.         J  f 

The  stratum  corneum  consists  of  old,  exhausted,  flattened,  and 
desiccated  cells,  which  are  constantly  falling  from  the  entire  sur- 
face of  the  body.  Dandruff  consists  of  impacted  cells  from  this 
source.  Those  portions  most  frequently  exposed  to  friction  —  e.g., 
the  palms  of  the  hands  and  the  soles  of  the  feet  —  are  protected  ~by 
a  corneous  epidermal  layer  of  great  thickness. 

The  stratum  lucidum,  or  clear  layer,  presents  cells  in  form  not 
unlike  those  in  the  preceding  stratum  ;  they  are,  however,  trans- 
lucent. This  is  properly  a  part  of  the  previous  stratum,  is  often 
absent,  and  frequently  very  difficult  of  demonstration.  The 
stratum  lucidum  and  stratum  corneum  owe  their  characteristic 
properties  largely  to  the  development  in  their  cells  of  a  substance 
called  keratin. 

The  stratum  granulosum,  or  granular  layer,  is  composed  of 
flattened  cells  containing  opaque  granules  of  eleidin,  which  is 
related  to  the  keratin  of  the  horny  layers. 

Immediately  beneath  the  last-named  layer,  the  cells  become 
strikingly  altered  in  form  and  appearance.  The  pricUle  cells  are 

(92) 


THE    SKIN 


93 


polygons  or  compressed  spheroids,  with  large,  oval  nuclei,  and 
minute,  projecting  spines.  By  means  of  these  processes  they  are 
connected  with  one  another. 

The  fifth  and  last  (deepest)  layer  of  the  epidermis  is  composed 
of  a  single  rank  of  elongated  cells,  placed  with  their  long  axes  lit 
a  right  angle  to  the  surface  of  the  skin.  These  cells  contain  the 


FIG.    66.     VERTICAL  SECTION  OP   THE  EPIDERMIS  FROM  THE   PALM  OP   THE    HAND. 
STAINED  WITH  H^EMATOXYLIN  AND  EOSIN.     (X  400.) 

A.  Stratum  corneum. 

B.  Stratum  lucidum. 

C.  Stratum  granulosum. 

D.  Prickle  cells  of  rete  mucosum  or  rete  Malpighii. 

E.  Stratum  of  elongated  cells,  the  lower  limit  of  the  epidermis. 

F.  F.    Indicate  the  position  of  two  papillae  of  the  true  skin  or  derma. 

pigment  which  gives  the  hue  peculiar  to  the  skin  of  colored 
individuals. 

The  first  two  layers  of  the  epidermis  constitute,  properly,  the 
horny  layer  ;  while  the  remaining  three  strata  compose  the  rete 
mucosum  or  rete  Malpigliii. 

The  derma,  corium  or  true  skin,  is  composed  of  dense,  fibril- 
lated  connective  tissue,  so  formed  as  to  present  minute  elevations 
or  papillae  over  the  entire  surface  of  the  body.  These  papillae  are 


94 


HJSTOLOG Y 


covered  with  a  basement  membrane,  and  are  protected  from  undue 
irritation  by  the  epidermal  layers. 

The  subcutaneous  cellular  tissue  (upon  which  the  true  skin 
rests)  consists  of  fibrillated  connective  tissue  with  elastic  ele- 
ments, from  which  strong  interlacing  bands  are  formed.  These, 
in  the  deeper  parts,  form  septa  which  support  lobules  of  adipose 
tissue.  These  isolated  collections  of  adipose  tissue,  when  elon- 
gated and  placed  vertically  to  the  surface,  constitute  the  fat- 
columns. 


FIG.   67.     VERTICAL   SECTION   SHOWING   THE   DERMA,  OR  TRUE   SKIN.      INJECTED— 
PARTLY  DIAGRAMMATIC. 

A.  Line  of  junction  of  derma  with  epidermis. 

B.  Capillaries  distributed  to  papillae. 

The  blood-vessels  supplying  the  skin  may  be  seen  in  vertical 
sections,  in  the  subcutaneous  tissue.  Branches  from  these  are 
sent  to  the  papillae,  where  they  terminate  in  delicate,  interlacing 
loops  of  capillaries. 

Medullated  nerves  are  also  sent  to  the  papillas ;  and  in  certain 
locations  they  may  be  seen  to  terminate  in  tortuous  structures — 
the  tactile  corpuscles.  Varicose  nerve- fibrils  have  been  traced 
between  the  cells  in  the  rete  mucosum  of  the  epidermis. 


SKIN— HAIR  95 


APPENDAGES    OF   THE   SKIN 

The  appendages  of  the  skin  are  the  hairs,   sebaceous  glands, 

sudoriferous  glands,  and  the  nails. 

t 

THE     HAIR 

A  hair,  consisting  of  a  root  and  shaft,  is  constructed  from 
elongated,  often  pigmented  cells,  which  are  cemented  together 
and  overlapped  with  cell -plates,  which  form  the  cuticle.  The 
central  part  of  medullated  hairs  is  composed  of  cubical  cells  and 
occasional  minute  air -bubbles. 

The  root  penetrates  the  stratum  corneum  and  (appearing  to 
have  pushed  the  rete  mucosum  before  it)  passes  through  the  true 
skin  and  terminates  in  a  bulb  usually  in  the  subcutaneous  tissue, 
where  it  rests  upon  a  papilla  composed  of  an  extremely  delicate 
plexus  of  blood -capillaries. 

The  Hair- Follicle. — The  root  of  the  hair,  in  its  passage  to  the 
papilla,  is  invested  with  sheaths  derived  from  the  skin.  The  hair, 


E 

FIG.  68.    TRANSVERSE  SECTION  OF  HAIR  AND  HAIR-FOLLICLE. 
PARTLY  DIAGRAMMATIC. 

A.  Medulla  of  hair. 

B.  Cortex  of  same. 

C.  Root-sheath. 

D.  Glassy  membrane. 

E.  Fibrous  wall  of  the  follicle. 

with  its  follicle,  is  indicated  in  transverse  section  in  Fig.  68.  A 
represents  the  medulla,  and  B  the  cortex  of  the  hair.  Outside  the 
root-sheath,  C,  and  derived  from  the  rete  mucosum  of  the  epider- 
mis, is  a  thin  layer,  the  glassy  membrane,  D.  This  is  projected 
from  the  basement  membrane  covering  the  surface  of  the  corium, 


96 


STUDENTS   HISTOLOGY 


or  true  skin.     The  whole  is  surrounded  by  a  fibrous  coat,  E,  de 
rived  from  the  connective  tissue  of  the  derma. 

A  vertical  section  of  the  follicle  is  indicated  in  Fig.  69.    A,  B, 
and  C  represent  the  epidermal  layers,  which  do  not  enter  into  its 


FIG.  69.    DIAGRAM  SHOWING  MODE  OF  FORMATION  OF  HAIR-FOLLICLE 

A'.  Epidermal  layers. 
B'.  Derma,  or  true  sftin. 

A.  Horny  layer  of  epidermis. 

B.  Stratum  lucidum. 

C.  Stratum  granulosum. 

The  three  last  mentioned  form  no  part  of  the  follicle. 

D.  Rete  Malpighii.    This  will  be  seen  projected  into  the  depths  of  -the  true  skin  to  form 
Ihe  root-sheath,  G. 

E.  Hyaline  membrane  covering  the  derma.    This  is  projected  into  the  follicle,  forming  the 
glassy  membrane,  H. 

F.  Fibrous  tissue  of  the  derma,  forming  the  fibrous  sheath  of  the  hair-follicle,  I. 

G.  Root-sheath  of  the  hair-follicle. 
H.  Glassy  membrane  of  the  follicle. 
I.     Fibrous  sheath  of  the  follicle. 

J.    The  hair-follicle. 

composition.  The  rete  mucosum,  D,  forms  the  root-sheath  at  G. 
The  basement  membrane  of  the  corium,  E,  forms  the  glassy  mem- 
brane, H,  while  the  connective  tissue,  F,  constitutes  the  fibrous 
layer  of  the  hair -follicle,  J.  The  scales  lining  the  hair-follicle 
are  imbricated,  and  are  directed  downwards,  fitting  over  the 
scales  covering  the  surface  of  the  hair,  which  are  directed  up- 
wards, and  also  imbricated. 


MUSCLES     OF     THE     HAIR -FOLLICLES 

Attached  to  the  fibrous  layer  of  each  hair -follicle  is  a  small 
band  of  involuntary  or  smooth  muscular  fiber — the  arrector  pili. 
This  passes  obliquely  toward  the  surface  of  the  skin;  and  when 
contraction  takes  place,  the  follicle  and  hair  are  elevated,  producing 
the  phenomenon  known  as  goose-flesh. 


SUDORIFEROUS    GLANDS 


SUDORIFEROUS    OR    SWEAT-GLANDS 


97 


A  sweat-gland  (Figs.  67  and  70)  consists  of  a  tube  or  duct 
which,  from  the  opening  upon  the  surface,  passes  in  a  spiral 
course  through  the  several  layers  of  the  skin  to  the  deeper  part 
of  the  corium,  where  it  becomes  coiled  in  a  bunch,  as  at  D, 
Fig.  70.  The  coiled  or  glandular  part  of  the  tube  is  surrounded 
by  a  net -work  of  capillaries.  At  B  the  tube  is  seen  in  transverse 
section.  The  gland -tube,  D,  is  provided  with  a  wall  of  connec- 
tive tissue  and  smooth  or  involuntary  muscle,  lined  with  conical 


FIG.  70.  SUDORIFEROUS  TUBULAR  GLAND. 

A.  Diagrammatic  sweat-gland.    C.  Its  duct.    D.  Coiled,  glandular  part. 

B.  The  same,  showing  a  transverse  section  of  both  parts  (X  400).     C'.    The  duct  lined 
with  several  layers  of  cells.    D'.  The  coiled  glandular  part  lined  with  columnar  cells  in  a 
single  layer,  resting  on  a  basement  membrane. 

cells.  The  duct,  C,  is  lined  with  granular  epithelium  covered 
with  a  thin  cuticular  membrane.  Near  the  surface  of  the  epider- 
mis the  lining  cells  disappear. 

Krause   estimated   the  number  of   sweat-glands   at   over   two 
million. 


98 


STUDENTS    HISTOLOGY 


SEBACEOUS    GLANDS 

These  glands  are  little  sacs  or  lobules,  one  or  more  of  which 
open  into  each  hair -follicle.  These  sacs  are  entirely  filled  with 
polyhedral  epithelial  cells  (vide  Fig.  71) .  At  the  neck  of  the  gland 


FIG.  71.     SINGLE  LOBULE  OF  A  SEBACEOUS  GLAND  (X  400). 

A.  The  fibrous  wall  of  the  sac. 

B.  Membrane  propria. 

C.  Polyhedral  cells  filling  the  sac  completely. 

D.  Fatty  degeneration  of  the  parenchyma  at  the  neck  of  the  gland,  formation  of  sebum. 

the  cells  become  granular,  fatty,  and  disintegrated,  producing  the 
sebum. 

THE    NAILS 

The  peculiar  tissue  of  the  nails  corresponds  to  the  stratum 
lucidum  of  the  epidermis  developed  to  an  extreme  degree.  The 
nail  rests  upon  a  nail -bed,  which  represents  the  corium  and  the 
Malpighian  layer  of  the  epidermis.  Minute  longitudinal  ridges 
take  the  place  of  papillae.  The  root  of  the  nails  is  imbedded  in  a 
part  of  the  nail -bed  called  the  matrix,  from  which  its  growth 
occurs. 

PRACTICAL    DEMONSTRATION 

Remove  the  skin  from  the  parts  below  as  soon  after  death  as  practicable. 
Tissue  may  frequently  be  secured  after  surgical  operations  from  stumps,  etc. 
Dissect  deeply,  so  as  to  preserve  the  subcutaneous  tissue.  Small  cubes  from 
the  finger-tips,  the  palm  of  the  hand,  the  scalp,  and  the  groin  may  be  hardened 
quickly  in  strong  alcohol;  and  vertical  sections  should  be  made  as  soon  as  the 


THE   SKIN  99 

tissue  has  become  sufficiently  firm.     Stain  with  haBmatoxylin  and   eosin,  and 
mount  in  balsam. 

The  structure  of  hairs  may  be  best  demonstrated  by  washing  the  soap  from 
lather,  after  shaving,  with  several  changes  of  water.  When  clean,  decant  the 
water  and  add  alcohol.  After  twenty-four  hours  again  decant  and  add  oil~of 
cloves.  With  a  pipette  carry  a  drop  of  the  oil  with  the  deposited  hair-cuttings 
to  a  slide,  remove  as  much  of  the  oil  as  possible  with  slips  of  blotting-paper, 
and  mount  in  balsam.  Oblique,  vertical,  and  transverse  sections  maybe  readily 
obtained  by  this  method. 


VERTICAL     SECTION    OF     SKIN    FROM    THE     GROIN 

(Vide  Fig.  72) 

OBSERVE  : 
(L.)* 

1.  The  horny  layer  of  the  epidermis.     (The  stratum  lucidum 
will  hardly  be  demonstrable  on  account  of  the   thinness   of   the 
epidermis  in  this  region.) 

2.  The  rete  mucosum.   (The  section  from  which  the  illustration 
has  been  drawn  was  taken  from  a  negro,  and  the  deep  cells  were 
pigmented.) 

3.  The  sharp  line  of  demarcation  between  the  epidermis  and 
the  true  skin. 

4.  The  papillae  of  the  corium  or  derma.     (Note  the  absence  of 
any  sharp  line  dividing  the  corium  and  subcutaneous  tissues.) 

5.  The    larger   blood-vessels    of    the    subcutaneous    region. 
(The  arteries  in  transverse  sections  are  plainly  indicated  by  their 
prominent  media,  the  appearance  of  the  fenestrated  membrane  as 
a  wavy  yellowish  line,  and  by  the  elliptical  or  circular  outline. 
The  veins  are  smaller,  with  thinner  walls,  and  their  outline  is  gen- 
erally irregular.     The  smaller  veins  are  commonly  overlooked,  on 
account  of  their  lumen  having  become  obliterated  by  contraction  of 
the  tissue  in  hardening. 

6.  Coils  and  ducts  of   sweat-glands  in  subcutaneous  region. 
(The  tubes  are  cut  in  various  directions,  and  the  whole  is  sur- 
rounded by  dense  fibrous  tissue,  forming  a  kind  of  capsule.) 

7.  The  subcutaneous  collections  of  adipose  tissue  beneath  the 
last  region.     (The  septa  are  dense  and  strong.) 

8.  (Having   selected   a   vertical    section    of    a    hair-follicle: ) 
(a)  The  root  of  the  contained  hair.     (&)  The  bulb  and  the  hair- 
papilla,     (c)  The  medulla  of  the  hair,     (d)  The  root-sheath  pro- 
longed from  the  rete  mucosum.     (e)  The  fibrous  (outer)  sheath. 

*Low-power — i.  e.,  from  thirty  to  sixty  diameters. 


100 


STUDENTS  HISTOLOGY 


9.  The  sebaceous  glands.  (The  demonstration  of  the  connec- 
tion between  the  neck  of  the  gland  and  the  follicle  will  require  a 
very  favorable  section.) 

10.   (Scattered    through   the   corium   and    upper    subcutaneous 


Fig.  72.    VERTICAL  SECTION  OF  SKIN  FROM  THE  GROIN.     STAINED  WITH 

H^EMATOXYLIN   AND   EOSIN. 

A.  Epidermis. 

B.  Deep,  elongated  cells  of  the  rete  mucosum. 

C.  C.    Papillae  of  true  skin. 

D.  D.    Subcutaneous  areolar  tissue. 

E.  E.    Collections  of  adipose  tissue. 

F.  Shaft  of  hair  (obliquely  sectioned). 

G.  Root-sheath  of  hair. 
H.    Fibrous  sheath  of  hair. 

I.      Hair-papilla  (vertical  section). 

J.  J.  J.    Portions  of  sebaceous  glands  (one  on  the  extreme  right  of  the 

cut  is  seen  in  connection  with  the  hair- follicle.) 
K.  K.    Arrectores  pili. 

L.    Hair- follicle  with  contained  shaft  of  hair  in  very  oblique  section. 
M.  M.    Coils  of  sudoriferous  glands. 
N.    Spiral  duct  of  last. 
O.  O.    Arteries  of  subcutaneous  plane. 

region:)  (a)  Small  portions  of  sebaceous  glands.  (&)  Ducts  of 
sudoriferous  glands,  (c)  Oblique  sections  at  various  angles  of 
hair-follicles,  (d)  Small  vessels. 


THE    SKIN  101 

11.  Arrector  pili  mtiscle.     (Nearly  always  to  be  found  stand- 
ing obliquely  to  the  divided  hair -follicle. 

(H.)* 

12.  (If  demonstrable:)    (a)  The  stratum  lucidum.     (b)  Stra- 
tum granulosum. 

13.  The  columnar  cells  of  the  rete,  next  the  corium. 

14.  (Where  the  tissue  has  been  torn:)   The  impacted  cells  of 
the  horny  epidermis. 

15.  The  basement  membrane  covering  the  corium. 

16.  Capillaries  of  the  papillae  of  the  corium.     (These  may  be 
distinguished,    when    seen    longitudinally,    by   tortuous    lines    of 
elongated  and  deeply  stained  nuclei  belonging  to  their  endothelium. 
Arterioles  may  be  differentiated  by  their  long  muscle  cells,  the  cir- 
cular fibers  lying  transversely  to  the  vessel.) 

17.  The  root-sheath  of  the  hair-follicles.      (The  cells  compos- 
ing the  root -sheath  vary  in  appearance,  according  to  their  position 
relatively  to  the  hair;   and  this  will  enable  you  to  demonstrate  two 
layers,  or  an  inner  and  an  outer  root -sheath.) 

18.  The   glassy  membrane   of   the    hair-follicle.     (Appearing 
simply  as  a  clear  space  between  the  root -sheaths  and  the  outer 
fibrous  coat.) 

19 .  The  intra-cellular  network  in  the  large  polyhedral  epithelial 
cells  of  the  sebaceous  glands,  and  the  minute  fat- globules  in  the 
same. 

20.  The  nuclei  of  the  fat-cells  in  the  adipose  tissue.     (They 
appear  pressed  to  one  side.) 

21.  Medullated  nerve-bundles  in  transverse  or  oblique  section. 

*High-power — i.  e.,  from  three  hundred  to  four  hundred  diameters. 


102      .  STUDENTS  HISTOLOGY 

THE    CIRCULATORY    SYSTEM 
THE    HEART 

The  muscle  of  the  heart  has  already  been  described.  The 
muscle-cells  are  supported  by  a  small  amount  of  connective  tissue, 
in  which  run  the  blood- and  lymphatic  vessels  and  nerve -fibers. 
Both  medullated  and  non-medullated  nerve-fibers  are  supplied  to 
the  heart,  and  minute  ganglia  also  occur,  especially  in  the  auriculo- 
ventricular  and  the  inter -ventricular  furrows. 

The  PERICARDIUM  is  one  of  the  great  serous  membranes.  Its 
surface  is  covered  by  a  single  layer  of  flat  endothelial  cells,  beneath 
which  is  a  stratum  of  fibro- elastic  connective  tissue.  This  con- 
nective tissue  is  continuous  with  that  running  between  the  muscle- 
fibers.  Underneath  the  pericardium  there  is  usually  more  or  less 
adipose  tissue,  especially  along  the  course  of  the  larger  blood* 
vessels. 

The  ENDOCARDIUM  is  covered  with  a  single  layer  of  flat  endo- 
thelial cells,  which  rest  upon  fibro -elastic  connective  tissue.  The 
connective  tissue  is  continuous  with  that  supporting  the  muscle- 
fibers,  and  also  joins  with  the  lining  of  the  blood-vessels  that  open 
into  the  heart. 

The  valves  of  the  heart  are  duplications  of  the  pericardium, 
containing  abundant  connective  tissue.  The  muscle -fibers  of  the 
auricle  extend  a  short  distance  into  the  auriculo- ventricular  valves. 
A  few  blood-vessels  may  be  present  at  the  attached  borders  of  the 
valves. 

BLOOD-  VESSELS 

Blood-vessels  include  arteries,  arterioles,  capillaries,  venules,  and 
veins.  They  are  all  lined  with  flattened  endothelial  cells  cemented 
by  their  edges;  and  their  walls  are  constructed  from  non- striated 
muscular,  yellow  elastic,  and  fibrous  connective  tissues,  in  propor- 
tions varying  according  to  the  size  and  function  of  the  vessel. 
Arteries  are  active,  while  the  veins  are  comparatively  passive 
agents  in  the  circulation  of  the  blood. 

The  large  arteries  are  eminently  elastic,  from  preponderance  of 
yellow  elastic  tissue;  while  the  arterioles  are  eminently  contractile, 
from  excess  of  muscular  fiber. 


BLOOD-  VESSELS 


103 


Arteries  possess  three  coats:  the  intima  (internal),  media  (mid- 
dle), and  adventitia  (external). 

Fig.  73  represents  a  medium  -  sized  typical  artery.  The  intima, 
or  internal  coat,  A,  B,  C,  consists  of  a  layer  of  flattened  endo- 
thelial  cells,  which  rest  upon  fibrous  connective  tissue,  with  a  few- 
elastic  fibers.  These  structures  are  surrounded  by  a  layer  of  elastic 
tissue,  the  elastic  lamina  or  fenestrated  membrane,  which  is  the 
external  limit  of  the  intima.  It  appears  in  a  transverse  section  as 
a  wavy  (from  contraction  of  the  media)  shining  line,  and  is  an 
important  element,  from  its  relation  to  certain  abnormalities  of  the 
blood-vessels.  The  media,  D,  consists  of  alternate  layers  of 


FIG.  73. 


PARTLY 


TRANSVERSE  SECTION  OF  A  MEDIUM-SIZED  ARTERY. 
DIAGRAMMATIC. 

A.  The  endothelial  cells  in  profile. 

B.  Elastic  and  connective  tissue  supporting  the  endothelinm. 

C.  The  internal  elastic  lamina  or  fenestrated  membrane.    A,  B,  and  C  constitute  the  INTIMA 
of  the  artery. 

D.  The  MEDIA.    It  consists  of  muscular  and  elastic  tissues  in  alternating  layers. 

E.  Points  to  one  of  the  elastic  layers. 

F.  The  ADVENTITIA.    Loose  connective  tissue,  with  few  elastic  fibers. 

elastic  and  muscular  tissue.  The  adventitia,  F,  is  composed  of 
fibrous  connective  tissue,  containing  some  elastic  elements. 

As  we  approach  the  larger  arteries,  the  muscular  tissue  <jjmin- 
ishes  in  quantity  and  the  elastic  tissue  is  increased.  On  the  other 
hand,  the  elastic  element  diminishes  with  preponderance  of  muscle 
as  we  approach  the  smaller  arteries,  until  we  meet  the  arterioles, 
the  walls  of  which  are  made  almost  exclusively  of  involuntary  mus- 
cular fibers,  surrounding  a  layer  of  endothelial  cells. 

The  walls  of  the  capillaries  consist  of  a  single  layer  of  flat- 
tened endothelial  cells  cemented  by  their  edges.  The  union  is  not 


104 


STUDENTS   HISTOLOGY 


quite  continuous,   as  minute  openings   are   to   be   seen  at  irreg- 
ular intervals.* 

The  AORTA  has  intima,  media,  and  adventitia  like  the  other 
arteries.  The  preponderance  of  the  elastic  tissue  over  the  muscular, 
which  is  characteristic  of  large  arteries,  reaches  its  fullest  develop- 
ment in  the  aorta.  The  intima  is  thick,  and  is  not  well  marked  off 
from  the  media.  The  great  amount  of  elastic  tissue  in  large 
arteries  is  connected  with  their  function  of  converting  the  pulsating 
blood -current  into  a  steady  stream.  The  muscular  fibers  serve  to 
control  the  calibers  of  arteries  and  the  amount  of  blood  flowing  to 
any  part. 


FIG.  74.     ISOLATED  BLOOD-CAPILLARIES. 

A.  Plexus  from  a  pulmonary  alveolus,  stained- with  silver  (X  350). 

B.  Capillary  from  omentum,  stained  with  silver  and  haematoxylyi  (X  700). 

In  A  the  cells  are  outlined  by  the  silver ;  while  in  B  the  nuclei  in  addition  are  brought  out 
by  the  hsematoxylin. 

The  walls  of  veins  are  much  thinner  than  those  of  arteries. 
The  intima  presents  an  endothelial  lining,  but  the  line  of  demarca- 
tion between  this  coat  and  the  media  is  often  indistinct.  The 
media  contains  muscular  tissue  but  not  much  elastic  tissue;  and 
the  Adventitia,  usually  the  most  prominent  of  the  three  coats,  is 
composed  largely  of  fibrous  connective  tissue. 

The  valves  of  the  veins  are  reduplications  of  the  intima,  having 
a  semilunar  form,  and  with  the  fibrous  tissue  well  developed. 

*It  is  probable  that  what  appear  to  be  openings  between  endothelial  cells  are,  in  fact,  occu- 
pied by  cement  substance.  In  conditions  of  congestion  and  inflammation  they  become  actual 
holes,  and  facilitate  the  migration  of  the  leucocytes  from  the  vessels  by  their  amo?boid  move- 
ment, and  permit,  also,  the  diapedesis  or  escape  of  red  corpuscles  without  rupture  of  blood, 
vessels.— (Klein.) 


DEVELOPMENT    OF   CAPILLARIES  •  105 

Vnsa  vasorum  are  small  blood-vessels  which  serve  to  nourish  the 
outer  layers  of  the  large  arteries  and  veins. 

^PRACTICAL     DEMONSTRATION 

Sections  of  heart  showing  pericardium  and  endocardium,  of  aorta,  of  another 
large  artery,  and  a  large  vein,  should  be  studied  and  drawn.  The  small  blood- 
vessels will  be  encountered  in  the  various  organs. 

The  DEVELOPMENT  of  capillaries  is  important  because  the  larger 
vessels  first  appear  in  the  embryo  as  capillaries,  around  whose 
endothelium  the  other  coats  later  become  differentiated  from  the 
neighboring  mesoderm.  Areas  of  mesoderrnic  cells  branch,  unite 
with  one  another,  and  become  hollowed  out  to  form  a  system  of 
channels.  Part  of  the  protoplasm  and  nuclei  form  nucleated  red 
blood -corpuscles;  part  of  them  lie  outside  and  constitute  the  wall 
of  endothelial  cells  and  their  nuclei.  Later  in  embryonic  life  and 
after  birth  the  formation  of  capillaries  is  carried  on  in  much  the 
same  way,  and  becomes  of  great  importance  in  many  pathological 
processes  where  new  capillaries  are  required;  for  instance,  in  the 
healing  of  a  wound.  In  these  cases  solid  protoplasmic  outgrowths 
are  protruded  from  the  endothelial  cells  of  existing  capillaries. 
These  outgrowths  lengthen  by  multiplication  of  the  endothelial  cells 
or  by  fusion  with  connective  tissue  cells.  They  branch  and  also 
unite  with  other  similar  outgrowths  to  form  a  network.  Vacuoles 
appear  in  the  middle  of  the  processes,  which  enlarge,  become  con- 
fluent, and  make  channels  through  them,  which  open  into  the 
original  capillaries.  The  protoplasm  and  nuclei  of  the  solid  sprouts 
form  the  endothelium  of  the  new  capillaries. 

The  newly  forming  capillaries  may  be  studied  in  the  thin  tail  of  the  young 
frog-tadpole.  Select  a  tail  with  as  little  pigment  as  possible;  harden  in 
Flemming's  chromic -acetic  solution;  wash  thoroughly;  stain  with  haematoxylin 
and  eosin;  alcohol;  oil  of  cloves;  balsam.  Focus  on  a  plane  below  the 
epithelium  of  the  skin.  The  capillaries  are  narrow,  dark  bands,  with  nuclei; 
the  large  ones  containing  blood-corpuscles,  the  small  ones  solid  and  showing 
branches. 


106  STUDENTS  HISTOLOGY 


THE   LYMPHATIC    SYSTEM 

The  Lymphatic  System  is  a  circulatory  apparatus  of  exceed- 
ingly complicated  arrangement.  It  comprises  : 

1.  A  system  of  irregular  clefts  and  cavities  which  are  of  almost 
universal  distribution  in  the  more  solid  tissues,  in  the  framework 
and  parenchyma  of  organs,  and  around   blood-vessels  and  viscera. 
They  are  called  lymph -spaces  or  juice -canals. 

2.  Nodules  of  sponge-like  tissue,   improperly  called  lymphatic 
glands. 

3.  Channels  of  communication,   consisting   of   capillaries    and 
larger  vessels  called  lymphatics. 

4.  A  central  reservoir — the  receptaculum  chyli. 

5.  Large  efferent  lymphatics,  by  means  of  which  the  contents 
of   the  system  are,   eventually,   poured   into    the   blood,   in  both 
sides  of  the  neck  at  the  junction  of  the  internal  jugular  and  sub- 
clavian  veins. 

6.  A  fluid,   lymph,   containing  numerous   lymphoid  cells,    and 
various  substances  in  solution. 

The  whole  provides  a  channel  for  introducing  formed  and  nu- 
trient elements  into  the  blood,  and  for  conveying  nutrition  to  the 
cells,  as  well  as  affording  drainage  for  the  tissues,  the  products 
of  which  are  also  emptied  into  the  blood -vascular  system,  to  be 
afterward  eliminated  by  special  organs. 

The  circulating  lymph  always  passes  in  a  direction  toward  the 
venous  system.  This  current  is  established  in  some  of  the  lower 
animals  by  means  of  distinct,  pulsating,  hollow  organs,  or  lymph- 
hearts;  but  no  corresponding  structure  exists  in  man,  and  the  sys- 
tem becomes  here  subordinated  to  the' blood -vascular  apparatus. 

In  man,  the  maintenance  of  the  lymph- flow  is  due  largely  to  a 
negative  pressure,  consequent  upon  the  connection  between  the 
termini  of  the  lymph -vessels  and  the  veins.  Without  doubt  the 
pumping  motion  of  the  intestinal  villi  presents  a  factor  in  the 
establishment  of  a  current  in  the  lacteals  toward  the  mesenteric 
vessels.  The  perivascular  lymph  receives  an  impetus  with  each 
cardiac  systole.  The  muscular  contractions  of  inspiration  con- 
tribute motility  to  the  contents  of  the  diaphragmatic  lymph -chan- 
nels, in  a  direction  against  gravity.  Indeed,  the  contractions  of 
nearly  every  muscular  fiber,  whether  skeletal  or  organic,  lend  their 
aid  to  lymph- propulsion. 


LYMPH-  CHANNELS 


107 


The  direction  of  the  lymph- current  is  determined  by  valves 
which  resemble  somewhat  those  of  the  veins. 

Cavities  lined  with  so-called  serous  membranes  may  be  consid- 
ered as  expanded  lymph -channels. 


LYMPH-  CHANNELS 

The  larger  and  more  regularly  formed  channels  for  lymph-cir- 
culation, such  as  the  mesenteric  arid  thoracic  ducts,  do  not  differ 
materially  in  structure  from  correspondingly  sized  veins.  The 
irregular  clefts  in  the  interstices  of  fibrous  tissues,  serving  as  the 
primitive  lymph -containing  channels,  will  be  repeatedly  noticed 
in  studying  the  various  organs.  Fig.  75,  although  purely  dia- 


INTIMA 

MEDIA 

ADVENTITIA 
rPEfWASCULAR 
(.    SPACE 


FIG.   75.     DIAGRAM.     ARTERY  IN   TRANSVERSE   SECTION,   SHOWING   THE 
PERI  VASCULAR  LYMPH-SPACE. 

grammatic,  will  serve  to  show  the  relation  of  this  system  to  the 
blood-vessels.  A  peri  vascular  lymphatic  channel  is  a  sort  of 
tubular  investment  of  the  blood-vessel,  lined  with  flattened  endo- 
thelium  sending  prolongations  inward;  these  prolongations  branch, 
and  are  finally  in  communication  with  a  layer  of  cells  covering 
the  adventitia.  In  this  manner,  in  close  apposition  to  parts  $f  the 
vascular  system,  a  system  of  channels  is  provided,  within  which 
the  lymph  may  slowly  percolate.  They  are  usually  found  about 
the  arteries  of  the  central  nervous  system. 

The  largest  lymph -spaces  in  the  human  bodjr  are  the  cavities 
of  the  peritoneum  and  pleurae.  They  are  in  connection  one  with 
the  other,  and  with  the  lymphatic  system  generally;  and  the 
channels  of  communication  between  the  great  abdominal  and 


108  STUDENTS  HISTOLOGY 

thoracic  lymphatic  cavities  are,  perhaps,  the  most  convenient  and 
typical  for  demonstration. 

LYMPHATIC    VESSELS     OF    THE     CENTRAL    TENDON    OF    THE 
DIAPHRAGM    (Figs.  76  and  77) 

Practical  Demonstration 

This  demonstration  should  be  made  with  tissue  from  the  rabbit,  inas- 
much as  the  slightest  decomposition  of  the  endothelium  would  be  fatal  to 
success. 

A  small  (preferably  white)  rabbit  should  be  quickly  killed  by  decapitation, 
and  immediately  suspended  by  the  hind  legs,  so  as  to  thoroughly  drain  the 
body  of  blood.  As  soon  as  the  blood  has  ceased  dripping,  open  the  thoracic 
cavity  by  slitting  up  the  skin  along  the  median  line,  pushing  it  to  the  sides 
and  removing  the  sternum.  In  this  operation  work  rapidly  and  avoid  soiling 
the  internal  parts.  Then  with  the  fingers  of  one  hand  raise  the  lungs  and 
heart  from  the  diaphragm,  and  with  a  large  camel's-hair  brush  proceed  to 
quickly,  and  quite  forcibly,  pencil  the  white,  glistening  surface  of  the  central 
diaphragmatic  tendon,  moistening  the  brush  from  time  to  time  in  the  lymph 
of  the  pleural  cavity.  Should  the  quantity  of  fluid  be  small,  add  a  little  dis- 
tilled or  previously  boiled  and  filtered  water.  The  object  of  the  brushing  is 
to  remove  the  endothelial  cells  which  cover  the  surface,  and  which  would 
otherwise  hide  the  lymph-spaces.  After  the  penciling,  drain  away  the  fluid 
and  pour  over  the  brushed  surface  a  one -fifth  per  cent,  .solution  of  nitrate  of 
silver.*  Allow  the  silver  solution  to  remain  for  twenty  minutes  in  contact 
with  the  tissue,  the  body  meanwhile  being  kept  away  from  the  bright  sunlight; 
then  pour  off  the  solution,  wash  the  surface  twice  with  distilled  water,  and 
afterward  allow  water  from  the  tap  to  flow  over  the  parts  for  at  least  five 
minutes. 

If  you  observe  the  directions  carefully,  the  surface  of  the  tendon  will  lose 
its  original  glistening  appearance  and  become  whitish  and  opaque. 

The  tendon,  or  such  portion  of  it  as  you  wish  to  preserve,  may  be  cut  out 
with  the  scissors  after  the  washing,  thrown  into  glycerin,  and  placed  in  the 
sunlight  until  the  surface  becomes  brown.  With  the  forceps  tear  off  small 
pieces  of  the  stained  side,  say  one -half  inch  square,  and  examine  in  glycerin, 
or  mount  them  permanently  in  the  same  medium. 

The  demonstration  of  the  channels  of  the  lymphatic  system  is 
based  upon  the  following : 

1^  Lymph -channels  are  always,  however  small  or  irregular, 
lined  wiih  flattened  cells  in  a  single  layer — i.  e.,  endothelium. 

2.  The  lining  cells  are  cemented   together  with  an  albuminous 
substance. 

3.  Nitrate  of  silver  combines  ivith  the  cement,  forming  albumi- 
nate  of  silver,  which  becomes  dark  brown  when  exposed  to  light. 

*  Water  which  has  been  well  boiled  in  a  clean  vessel,  and  afterward  carefully  filtered,  may 
generally  be  employed  in  histological  work  when  distilled  water  is  not  available. 


CENTRAL    TENDON    OF   THE   DIAPHRAGM  109 

If  you  have  been  successful,  the  silver  will  have  penetrated  the 
tendon  and  mapped  out  the  lymph -channels,  indicating  an  outline 
of  every  lining  cell  by  means  of  a  dark  border.  Failure  will  result 
only  from  non  -  attention  to  cleanliness  in  the  handling  of  the  tis^ 
sue,  in  which  case  the  silver  becomes  deposited  generally  over  the 
surface.  The  margins  or  outlines  of  the  cells,  it  must  be  remem- 
bered, are  stained  with  the  silver.  The  nuclei  may  be  demon- 
strated by  after -staining  with  borax -carmine.  The  mounting 
may  be  done  in  balsam,  although  the  elastic  fibers,  of  which  the 
matrix  of  the  tendon  is  composed,  will  become  stiff  during  immer- 
sion, and  show  a  tendency  to  curl  and  contract.  If  glycerin  be 
used  after  carmine  staining,  tissues  should  be  washed  thoroughly 
in  water,  subsequently  to  the  acid  alcohol,  transferred  to  equal 
parts  of  glycerin  and  water,,  and  allowed  to  remain  for  an  hour, 
at  least,  before  mounting. 

CENTRAL   TENDON    OF    THE    DIAPHRAGM.       SILVER  -  STAINING 

(Vide  Figs.  76  and  77) 

OBSERVE  : 
(L.) 

1.  The  division  of  the  specimen   into  dark  and  light  areas. 
(The  dark  areas  represent  the  more  solid  portions  of  the  tissue  or 
the  partitions  between  the  channels,  and  the  light  spaces  are  the 
lymph-  paths.) 

2.  The  lymph-paths — the   light  spaces.       (These    show,   with 
this  amplification,  as  irregular,  winding,  and  anastomosing  courses, 
marked  with  very  delicate  lace -like  tracery — the  silver  lines.) 

3.  Valves  of  the  lymph-paths.     (At  points,  the  paths  will  be 
crossed  by  dark  curved  lines.      These  are   imperfect  valves,   not 
unlike  a  single  cusp  of  an  aortic  valve.) 

(H.) 

4.  Outlines    of     the     cells     lining     the     larger     excavations 
(lymph -paths)   in  the  tissue..    (Note  that  the  cells  are  generally 
elongated   in  the  direction  of   the  lymph -path.      The    edges    are 
frequently  serrated.) 

5.  Stomata,  minute  openings  at  the  junction  of  several  cells. 

6.  The  construction  of  the  valves.     (These  are  curved  against 
the   rymph-flow,   and  covered  with  cells  like  other  parts  of   the 
channel.     Note  the  change  in  form  of  the  cells  approaching  and 
covering  the  valves.) 


110 


STUDENTS   HISTOLOGY 


7.  Elastic  fibers  of  the  more  solid  parts  of  the  tendon. 

8.  Lymph-capillaries.      (These  will  be  seen  in   the   partitions 
between  the  larger  paths.     In  places  they  may  be  observed  empty- 
ing into  the  paths,  and  again  will  appear  as  simple  cavities,  ac- 
cording to  the  manner  sectioned.) 

9.  The  deeper  capillaries.      (Careful  focusing  upon   the  por- 
tions of  the  tendon  which  appear  most  solid  will  reveal  minute 
cell -lined  channels  or  capillaries.      The  student  must  remember 


FIG   76. 


LYMPH-CHANNELS.     CENTRAL  TENDON  OF  DIAPHRAGM  OF   RABBIT. 
SILVER -STAINING  (X  60). 


The  dark  portions  represent  the  more  solid  portions  of  the  tissue. 

The  light  areas  are  the  lymph-channels  ;    the  direction  of  the  flow  is  shown  hy  the  arrows. 
The  minute  lines  in  the  lymph-spaces   are  the   silver-stained   cement   boundaries   of  the 
endothelial  cells  lining  the  channels. 

The  valves  appear  as  curved  lines  in  the  lymph-spaces. 

that  we  cannot  penetrate  tissues  with  the  microscope  to  any  con- 
siderable depth,  but  are  restricted  to  nearly  a  single  plane.  If  it 
were  possible  to  penetrate  with  the  eye  the  entire  thickness  of  the 
tendon,  we  might  trace  the  lymph -paths  or  channels  from  the 
abdominal  to  the  thoracic  surface.) 


LYMPHATIC   NODES    OR    GLANDS 


111 


LYMPHATIC   NODES 

At  numerous  points  along  the  course  of  lymphatic  vessels  they 
penetrate  small  nodules  of  so-called  lymphoid  or  adenoid  tissue, 
which  have  been  termed  lymphatic  glands.  They  are  frequently 
microscopic;  others  attain  the  size  of  a  large  pea.  They  secrete 
nothing,  hence  are  not  glands.  They  are  somewhat  sponge -like  in 
structure,  and  the  lymph  filters  slowly  through  them. 


FIG.   77.    A  SMALL  PORTION  OF  SPECIMEN  SHOWN  IN  FIG.   76,   MORE  HIGHLY 
MAGNIFIED  (X  350). 

A,  A,  A.   Large  lymph-channel. 

B.  Valve  in  the  course  of  last. 

C,  C,  C.    Lymph-capillaries  in  the  more  solid  parts  of  the  tendon. 

D.  Endothelial  cells  upon  which  a  large  amount  of  silver  has  deposited.     Failure  to  follow 
the  instructions  for  the  staining  frequently  results  in  a  like  deposition  of  silver  over  the 
whole  surface. 

Most  frequently  several  lymphatic  channels  enter  one  of  these 
larger  nodes,  while  perhaps  only  a  single  channel  leaves  it. 

The  histology  of  a  lymph -node  is  not  always  easily  compre- 
hended by  the  student,  and  we  have  endeavored  to  make  a  diagram 


112 


STUDENTS   HISTOLOGY 


(Fig.  78)  which  will  simplify  the  matter  somewhat.  It  is  enveloped 
by  a  capsule  of  connective  and  involuntary  muscular  tissue,  which 
sends  trabeculce  into  the  body  of  the  organ,  and  these  branching 
posts  support  the  structure  as  a  framework.  The  interstices  are 
quite  small  in  the  more  central  portion  and  larger  toward  the 


FIG.  78.     DIAGRAM.     PERIPHERAL,  PORTION  OF  A  LYMPH-NODE. 

A,  A.  Afferent  lymph-vessels. 

B.  Capsule  of  the  node,  with  lymph -spaces  C,  C. 

D.  Trabecula  of  connective  tissue. 

E,  E,  E.  Lymph-path  in  the  node. 

F.  F.   Lymph-follicle  of  the  cortex. 

G,  G,  G.  Lymphoid  cells  in  the  cell  network  of  the  paths. 
H,  H.  Blood-capillaries  of  the  follicles. 

The  arrows  show  course  of  lymph. 

periphery;  this  has  resulted  in  the  application  of  the  terms  medul- 
lary and  cortical  to  the  respective  parts.  The  nutrient  blood- 
vessels are  contained  in  the  framework.  The  compartments  contain 
the  structure  peculiar  to  the  lymphatic  system — viz.,  lymphoid  or 
adenoid  tissue. 


LYMPHATIC   NODES    OB    GLANDS  113 

Lymphoid  or  adenoid  tissue  consists  of  a  mass  of  flattened  cells, 
with  numerous  delicate  fibrillar  prolongations,  which  branch  and 
anastomose  so  as  to  form  an  interwoven  structure — the  adenoid 
reticulum.  Klein  regards  the  cells  as  forming  no  essential  part  of- 
the  structure,  but  considers  them  as  flattened  plates  attached  to  the 
fibrils.  The  meshes  of  the  adenoid  reticulum  are  in  connection 
with  the  fibers  of  the  trabeculae,  and,  with  the  exception  of  the 
portion  next  the  latter,  are  filled — crowded,  in  fact — with  countless 
small,  spherical  lymphoid  cells.  Those  portions  of  the  tissue  which 
contain  the  cells  are  termed  the  follicles  of  the  cortex  and  cords  of 
the  medulla. 

The  lymph -path  is  the  portion  between  the  fibrous  trabeculae 
and  the  follicles  and  cords. 

When  we  learn  that  the  trabeculae,  follicles,  cords,  and  lymph- 
paths  pursue  very  tortuous  and  branching  routes,  we  can  appreciate 
the  complexity  of  the  organ  as  a  whole. 

The  blood-vessel  arrangement  presents  no  anomalies.  The 
small  arterial  trunks  enter  within  the  trabeculae,  finally  break  into 
capillaries  which  supply  the  follicles,  cords,  etc.,  and  the  blood  is 
then  collected  by  the  venules  for  the  efferent  veins. 

There  is  a  depression  at  one  side  of  the  lymph -node  called  the 
hilum,  where  the  arteries  enter,  and  the  veins  and  efferent  lym- 
phatic leave  the  lymph -node. 

Small  diffuse  collections  of  adenoid  tissue  are  to  be  seen  in  many 
organs.  These  do  not  differ  essentially  from  the  tissue  just 
described,  excepting  that  there  is  no  definite  arrangement  of 
trabeculae  and  lymph -paths,  as  in  the  compound  lymph -node;  the 
lymph  simply  filters  through  the  reticulum,  the  same  being  a  part  of 
the  lymph -channel  system  of  the  tissue  in  which  the  adenoid  struc- 
ture may  occur. 

PRACTICAL     DEMONSTRATION 

The  mesenteric  lymphatic  nodes  present  the  most  typical  structure,  and  may 
be  obtained  from  the  human  subject,  if  fresh,  although  those  from  the  dog  are 
preferable,  on  account  of  the  better  condition  of  the  tissue  as  usually  secured. 

The  nodes  should  be  sliced  in  half,  placed  in  Miiller  for  a  week,  and  then 
hardened  by  two  days  immersion  in  strong  alcohol. 

Sections  should  be  mounted,  of  two  kinds,  viz.,  those  including  the  whole 
area  of  the  node— which  need  not  be  very  thin — for  demonstration  of  the 
scheme  or  plan  of  structure,  and  exceedingly  thin  ones,  even  though  they  may 
include  only  a  small  part  of  the  organ,  for  study  of  the  details  of  the  adenoid 
reticulum.  The  latter  purpose  will  be  subserved  by  shaking  a  number  of  thin 


114  STUDENTS  HISTOLOGY 

cuts  in  a  test-tube  with  alcohol  for  a  few  minutes,  and  with  considerable  vio- 
lence, even  sacrificing  most  of  the  sections.  The  agitation  will  dislodge  the 
lymph-cells,  which  otherwise  would  obscure  the  histology  of  the  lymph- 
follicles  and  cords. 

Stain  deeply  with  hsematoxylin  and  eosin,  and  mount  the  thicker  sections 
in  balsam,  and  those  especially  thin  in  glycerin. 


SECTION   OF   MESENTERIC   LYMPHATIC   NODE 

OBSERVE:  (Fi*s-  79  and  8°) 

(L.) 

1.  The   fibrous   capsule.      (Note   the   elongated   dots   in   the 


Fia.  79.    VERTICAL  SECTION  OF  A  LYMPH-NODE  FROM  THE  MESENTERY  (X  60). 

A.  Capsule  of  node. 

B.  Lymph-spaces  in  the  last. 

C.  C.  Trabeculse,  L.  S.     (Longitudinal  section.) 

D.  D.  Follicle,  L.  S. 

E.  Obliquely  sectioned  trabecula. 

F.  F.  Large  blood-vessels  of  the  central  portion  of  the  node. 

G.  Trabecula  in  T.  S.     (Transverse  section.) 

H.  Medullary  cord  in  T.  S.  I 

I.    Small  and  irregular  cords  of  the  center  of  the  node. 
J.    Obliquely  sectioned  trabecula  of  the  center  of  the  node. 
K,  K,  K.   Lymph-paths. 

deeper  parts  of  the  capsule — the  nuclei  of  the  smooth  muscular 
tissue,  the  thick- walled  arteries,  the  lymph-spaces.) 

2.  The  trabeculae.     (Trace  these  as  they  penetrate  the  organ, 
and  observe  that  they  frequently  end  abruptly,  on  account  of  hav- 


SECTION   OF  MESENTEEIC  LYMPHATIC   NODE 


115 


ing  curved,  so  as  to  leave  the  plane  occupied  by  the  section.     The 
trabeculae    are    not   partitions,  like   the   interlobular   pulmonary 
septa  or  the  prolongations  from  the  capsule  of  Glisson  in  the  liver; 
they  are  not  unlike  rods  or  posts,  making  a  framework  and  no 
producing  alveoli.     Find  one  divided  transversely.) 

3.  The  rounded  follicular  masses  of  lymphoid  or  adenoid  tissue 


FIG.  80.    FRAGMENT  OF  SECTION  SHOWN  IN  FIG.  79.'    MORE  HIGHLY 
MAGNIFIED  (X  350). 

A.  1'rabecula. 

B.  Lymphoid  cord. 

C.  Lymph-path. 

D.  Large  branching  cells  of  the  lymph-path. 

E.  Capillaries  of  the  cord. 

in  the  cortex,  and  the  cord-like  masses  of  it  in  the  medulla.    (They 
are  recognized  as  granular  areas  between  the  trabeculaa.) 

4.  The  lymph-paths.  (These  can  be  appreciated  by  remem- 
bering that  the  follicles  and  cords  do  not  entirely  fill  the  spaces 
between  the  trabeculae,  and  that  the  area  between  the  two — i.e., 
outside  the  cords — is  the  more  open  in  texture,  and  contains  the 
filtering  lymph.  They  are  more  distinct  in  the  cortex.) 


116  STUDENTS    HISTOLOGY 

(H.) 

5.  The  histology  of  the  capsule,     (a)  The  closely  united  con- 
nective tissue  with  the  scattering   elastic  fibers  of  the    external 
layer.      (b)   The    smooth   muscle    of   the  deeper   portions,     (c) 
Sections    of    arteries.       (These    may   be   of    considerable    size.) 
(d)   The  lymph-spaces.     (The  differentiation  is  by  the  flattened 
endothelial  cells  of  spaces  which  otherwise  would  be  supposed  mere 
rifts  in  the  tissue,  inasmuch  as  no  definite  or  special  wall  can  be 
detected.) 

6.  The    structural    elements   of   the   trabeculae.      (They   are 
similar   to  those  of   the  capsule,   excepting    the   elastic   element, 
which  cannot  here  be  demonstrated.     Note  the  variously  sectioned 
small  arteries.) 

7.  The    follicles    of   the   cortex   and   lymphoid    cords    of    the 
medulla.      (In   the   thicker  section,  the   field  will  be   completely 
crowded  with  lymphoid  cells.     Select  a  thin  field  and  observe:    (a) 
The  lymphoid  cells.     (These  will  be  found  varying  in  size  from  a 

.very  small  red  blood -disc  to  that  of  a  large  white  corpuscle;  the 
nucleus  is  usually  large,  single  or  otherwise,  while  the  protoplasm 
is  often  scanty.)  (&)  The  branching  endothelial  cells,  (c)  The 
delicate  fibrilla?  of  the  adenoid  reticulum.  (You  may  endeavor 
to  determine  whether  this  reticulum  exists  as  an  offshoot  of  the 
endothelial  cells,  or  whether  the  latter  are  simply  adherent  to  the 
•broadened  plates  of  the  former.) 

8.  The  reticulum  of  the  lymph-paths.     (Observe  that  this  is 
precisely  like  the  reticulum  of  the  follicles,  as  demonstrable  after 
shaking  out  most  of  the  lymph-corpuscles  of  the  last.)      (a)  The 
connection   between   the  fibrillae  of   the   paths  and   those    of 
'the   trabeculae. 

9.  Capillaries  of  the  paths  and  cords.     (These  will  be  recog- 
nizable only  by  the  regular  succession  of  the  contained  red  blood- 
corpuscles.) 


THE    SPLEEN  117 


THE    SPLEEN 

The  spleen  presents  no  regular  subdivision  of  parts  which  may_ 
be  studied  separately  and  combined  afterward,  as  we  are  able  to  do 
with  organs  like  the  lung,  liver,  etc.  The  spleen  is  a  ductless  organ 
or  so-called  gland,  and  the  plan  or  scheme  may,  perhaps,  be  best 
comprehended  by  following  the  blood  distribution. 

The  splenic  artery  enters  the  organ  at  the  hilum,  supported  by 
a  considerable  amount  of  connective  tissue,  and  rapidly  breaks  into 
smaller  branches,  from  which  the  arterioles  leave  at  right  angles. 
The  arterioles  quickly  merge  into  capillaries,  which  form  plexuses 

Capsule 

Traleculce 

Fein  ^^*^K-AJ^tf\AA*     Venous  spaces 

Spleen-pulp 
Capillaries 


FIG.  81.     DIAGRAM.     SHOWING  THE  COURSE  OF  BLOOD  IN  THE  SPLEEN. 

throughout  the  different  portions  of  the  organ.  Here  we  meet  with 
an  anomalous  structure. 

The  capillaries,  instead  of  uniting  to  form  venules,  as  in  the 
usual  vascular  plan,  empty  their  contents  into  small  chambers  or 
sponge -like  cavities — the  venous  spaces.  The  blood,  after  filtering 
through  the  venous  interstices,  is  collected  in  larger,  irregular, 
vein -like  channels,  which  finally  conduct  the  blood  into  the  veins 
proper  and  out  of  the  spleen.  The  tissue  containing  this  vascular 
arrangement  is  called  splenic  pulp. 

The  fibrous  capsule  which  envelops  the  spleen  sends  trabeculae 
within,  which  form  a  framework;  and  from  this  fibrils  are  sent  off, 


118  STUDENTS   HISTOLOGY 

which  branch,  broaden,  and  inosculate  to  form  the  supporting 
framework  of  the  pulp. 

The  arteries  are  frequently  surrounded  by  nodules  of  lymphoid 
(or  adenoid)  tissue,  sometimes  globular,  more  frequently  consider- 
ably elongated,  and  following  the  vessel  for  a  considerable  distance. 
These  nodules  are  called  MalpigJiian  bodies.  They  bear  no  resem- 
blance to  the  similarly  named  structures  in  the  kidney,  excepting, 
perhaps,  when  seen  in  transverse  sections  by  the  naked  eye. 

The  spleen  will  thus  be  seen  to  consist  of  fibrous  trabeculated 
framework,  the  pulp,  blood-vessels,  and  more  or  less  isolated  nodules 
of  lymphoid  tissue. 

PRACTICAL    DEMONSTRATION 

The  organ  must  be  perfectly  fresh.  If  human  tissue  cannot  be  obtained 
in  good  condition,  recourse  may  be  had  to  the  ox,  which  will  provide  an  ex- 
cellent substitute.  The  small  supernumerary  spleens,  not  infrequently  found 
during  post-mortem  work,  are  most  desirable,  as  sections  can  be  easily  made 
through  the  entire  organ. 

Pieces  of  tissue  a  centimeter  thick,  including  a  portion  of  the  capsule, 
should  be  hardened  as  directed  for  lymph-nodes.  Sections  are  easily  made 
without  the  microtome,  as  the  mass  is  very  firm;  they  should  be  thin  and 
stained  with  borax-carmine  or  hsematoxylin,  and  mounted  in  balsam. 


SECTION  OF  HUMAN  SPLEEN,  CUT  AT  A  RIGHT  ANGLE  TO  AND 
INCLUDING  THE  CAPSULE.   (Fig.  82) 

OBSERVE : 
(L.) 

1.  The  fibrous  capsule.     The  clear,  translucent  appearance  of 
its  elastic  tissue  and  the  elongated  nuclei  of   the   smooth  muscle- 
cells.     (The  capsule  not  infrequently  becomes  considerably  thick- 
ened in  the  human  subject,  and  the  development  occurs  irregularly, 
sometimes  in  the  form  of  minute  nodules.) 

2.  The  trabeculae.     (The  depth  to  which  they  may  be  traced 
will  depend  largely  upon  the  direction  of  the  section.)      (a)  That 
these  are  not  bands,  but  bundles,  more  or  less  circular  in  trans- 
verse section.      (6)   Their  irregular  course,  quickly  after  leaving 
the  surface,     (c)  That  occasionally  a  small  artery  may  be  found 
within  them,  though  they  are  usually  destitute   of   large  vessels. 
(d)  The  elongated  nuclei  of  the  muscular  fibers  forming  part  of 
the  trabeculag. 


SECTION    OF   HUMAN   SPLEEN 


119 


3.  The  large  blood-vessels,     (a)  The  arteries  more  frequent 
than   veins,      (b)    Their   very   prominent   adventitia.      (c)    Their 
tortuous  course. 

4.  The   lymphoid   (or   adenoid    tissue).      (This   you  will  be 
enabled  to  recognize  by  the  great  number  of  lymphoid  cells  of  the" 


FIG.  82.    SECTION  OF  THE  SPLEEN  (X  60). 

A.  Elastic  portion  of  the  capsule. 

B.  Lymph-spaces  of  last. 

C.  Involuntary  muscular  portion  of  capsule. 

D.  Deeply  pigmented  portions  of  capsule. 

E.  E.  Trabeculse  from  C. 

F.  Trabeculse  in  oblique  section. 

G.  G.  The  splenic  pulp. 

H,  H.  Large  arteries  in  T.  S. 

I.    Arteries  in  L.  S. 

J.    Adenoid  nodule,  not  connected  with  an  artery. 

K.   Adenoid  nodule— Malpighian  body— along  course  of  artery. 

L.  Adenoid  nodule  in  T,  S. 

M.  Vein. 

adenoid  structure,  the  nuclei  of  which  become  stained  very  deeply 
blue  with  haematoxylin,  giving  a >very  distinct  differentiation.  At 
this  point  examine  every  part  of  the  specimen  closely,  and  en- 
deavor to  detect  even  the  most  minute  collection  of  this  tissue.) 
(a)  Around  arteries,  constituting  the  so-called  Malpighian  bodies. 


120  STUDENTS    HISTOLOGY 

(b)  Transverse  sections  of  Malpighian  bodies,  noting  that  the 
vessel  is  seldom  in  the  center  of  the  nodule.  (<?)  Nearly  longi- 
tudinal section  of  Malpighian  nodules,  observing  that  the  lymph- 
oid  tissue  usually  follows  or  surrounds  the  artery  for  a  short 
distance  only.  In  many  of  the  lower  animals  the  Malpighian 
bodies  are  more  sharply  marked  off  from  the  splenic  pulp  than 
in  man. 

5.  The  Splenic  pulp.     (This  will  be  found  in  those  portions  of 
the  section  not  occupied   by  structures  previously  demonstrated ; 
and  wiH  be  determined  by  its  light  color.     Review  the  whole  area, 
and  endeavor  to  differentiate  every  portion  of  the  lymphoid  and 
pulp -tissue.     The    staining  will  have  been   your  principal  guide 
thus  far,  the  pulp-elements  appearing  in  strong  contrast  by  their 
pink  eosin  color.) 

(H.) 

6.  The  structural  elements  of  the  capsule,     (a)  The  numer- 
ous  minute  lymph-spaces  and   the   imperfect  vascular  supply. 
(b)  The  nuclei  of   the  peritoneal  cell  covering.      (This  presup- 
poses  that   the    section  has   been   selected  so    as    to    include    the 
peritoneal    investment.)       (c)   The    abundant   and   closely  packed 
connective  tissue,      (d)  The   muscle -nuclei,     (e)  Cells   contain- 
ing granular  yellow  pigment.     (The  quantity  varies  largely  with 
different  specimens.) 

7.  The  Malpighian   nodules,     (a)   The  arterioles — very  small 
and  apt  to  escape  attention  unless  filled  with  blood -corpuscles. 
(b)  Their  reticulum.     (This  will  be  difficult  of  satisfactory  dem- 
onstration, unless  the  section  is  thin.) 

8.  The  elements  of  the  pulp,     (a)  Large  flattened  cells,  the 
branches  forming  the  meshwork   of  venous  channels.      (b)   Red 
blood-corpuscles.   (Very  numerous,   and   often   broken    and   dis- 
torted.)      (c)    Blood -pigment.       (d)    White    blood-corpuscles. 
(Some   of    them    may  contain   granules    of    pigment,   which    are 
composed  of  the  derivatives  resulting  from  the  disintegration  of 
hasmoglobin.      The   destruction   of  worn-out  red  blood -corpuscles 
probably  is  one  of  the  most  important  functions  of  the  spleen.) 
(e)   Large   multi-nucleated    cells,   (which   are  commoner   in   the 
spleens  of  young  animals). 


THYMUS    BODY  121 


THYMUS   BODY 

The  thymus  body  (frequently  and  im property  called  a  gland)  is 
an  adjunct  to  the  lymphatic  system  of — in  man — foetal  and  infatiF 
tile  life,  disappearing  by  an  atrophic  process  at  or  before  the  age 
of  puberty. 

It  is  enveloped  by  a  fibrous  capsule,  partitions  from  which  sub- 
divide the  organ  into  lobes  and  lobules.  The  lobules  are  generally 
subdivided  into  follicles,  which  are  irregularly  sized  and  shaped, 
while  tending  to  an  ovoid  form. 

It  is  in  connection  with  the  general  lymphatic  system  by  efferent 
vessels  which  emerge  from  the  hili  of  the  lobes — the  lymph  having 
meanwhile  traversed  the  mesh -like  structure  of  adenoid  tissue 
composing  the  follicles. 

The  blood- vascular  system  is  in  the  form  of  a  nutritive  supply; 
the  larger  vessels  occupying  the  fibrous  framework,  and  sending 
branches  into  the  follicles.  The  capillary  plexuses  are  more  abun- 
dant in  the  peripheral  portion  of  the  follicles.  The  blood  is  col- 
lected in  the  venous  channels  of  the  central  or  medullary  area,  and 
emerges  from  the  organ  by  the  veins  which  accompany  the  efferent 
lymphatics. 

PRACTICAL    DEMONSTRATION 

The  organ  should  be  obtained  from  a  still-born  infant,  divided  in  small 
pieces,  and  hardened  rapidly  in  strong  alcohol.  Sections  may  include  an  entire 
lobe,  and  be  stained  with  haematoxylin  and  eosin. 


SECTION   OF   THE   THYMUS   BODY   FROM   AN   INFANT   AFTER 

DEATH   ON   THE   SIXTEENTH   DAY 
OBSERVE: 

(L.) 

1.  The  fibrous  capsule. 

2.  Division  by  prolongations  of  1  into  somewhat  spherical  lobes. 

3.  Subdivision  of  2  into  lobules. 

4.  Subdivision  of  3  into  follicles.     (Note  that  these  are  not 
uniformly  outlined  \)y  the  connective  tissue.) 

5.  The  subdivision  of  the  follicles  into  an  outer,  deeply  stained 
cortex,  which  completely  surrounds  a  light  center,  the  medulla. 

6.  The  larger  lymph-spaces  and  arteries  of  the  capsular  and 
trabecular  tissue. 

(H.) 

7.  The   cortex  of   the    follicles.      (a)   The    numerous    deeply- 


122 


STUDENTS  HISTOLOGY 


stained  lymph-corpuscles.  (6)  The  network  of  the  iymphoid  (or 
adenoid)  tissue.  (This  will  be  greatly  obscured  by  the  Iymphoid 
cells.)  (c)  The  blood-capillaries.  Only  recognized  by  the  con- 
tained corpuscles,  (d)  Minute  trabeculae  of  the  connective  tissue 
projected  from  the  capsule. 

8.  The  medulla  of  the  follicles,      (n)  The  sparsity  of  lymph- 
corpuscles  as  compared  with  the  cortical  portions,      (6)   Large 


FIG.  83.  — SECTION  OP  A  PORTION  OF  THE  THYMUS  BODY  FROM  A  CHILD  SIXTEEN 
DAYS  AFTER  BIRTH  ()<  t>0). 

A.  A.   Capsule  which  divides  the  organ  into  lobes.     Portions  of  six  lobes 

are  visible  in  the  section. 

B.  B.  Lymph-sp.aces. 

0.  C.    Trabeculze  dividing  the  lobes  into  imperfect  lobules. 

D.  D.  Subdivisions  of  the  last  into  follicles. 

E.  E.   Central  light  portion  of  the  lobules. 

mononucleated  cells.  (c)  Still  larger  multinucleated  cells. 
(d)  Larger — though  varying  in  size — spherical  bodies,  Hassall's 
corpuscles.  (These  are  composed  of  epithelial  cells,  arranged 
concentrically,  and  are  unlike  any  other  structure  found  in  the 
normal  tissues  of  the  body.  They  resemble  the  smaller  "cell- 
iiests  "  of  epithelioma.  The  corpuscles  of  Hassall  are  the  remains 
of  the  epithelial  structure,  which  makes  up  the  bulk  of  the  thy- 
mus  body  in  its  early  stages.)  (e)  Small  thin- walled  venules. 


THE   RESPIRATORY   ORGANS  123 


THE    RESPIRATORY    ORGANS 

The  larynx  and  trachea  have  the  same  general  structure  as  the 
larger  bronchial  tubes.  The  epithelium  is  stratified  columnar  and 
ciliated,  except  that  covering  the  surfaces  of  the  epiglottis  and  that 
of  the  upper  part  of  the  larynx,  which  is  stratified  squamous. 
The  cartilages  are  hyaline,  except  those  of  the  epiglottis,  part  of 
the  arytenoids,  and  the  cartilages  of  Wrisberg  and  Santorini,  which 
are  yellow  elastic  cartilage. 

THE   LUNGS 

At  the  root  of  each  lung  the  large  primary  bronchus  enters, 
and  divides  into  two  branches,  which  also  divide  and  branch 
repeatedly  until  terminal  or  capillary  bronchial  tubes  are  formed, 
which  are  one -fourth  to  one -eighth  of  a  millimeter  in  diameter. 

A  typical  bronchial  tube  (Fig.  84)  presents  four  coats,  as 
follows : 

1.  Epithelial. 

2.  Internal  fibrous  or  mucosa. 

3.  Muscular  or  muscularis  mucosce. 

4.  External  fibrous  or  submiicosa. 

The  lining  epithelium  is  composed  of  cylindrical  cells,  provided 
on  their  free  extremities  with  delicate  hair -like  appendages — the 
cilia.  Between  the  pointed,  attached  ends  of  the  ciliated  cells, 
small,  ovoid  cells  are  wedged,  and  the  whole  rests  upon  a  layer  of 
round  cells.  The  epithelium  pursues  a  wavy  course,  so  that  the 
lumen  of  a  tube  appears  stellate  rather  than  circular  in'  transverse 
section.  This  greatly  increases  the  extent  of  surface. 

The  internal  fibrous  coat  or  mucosa  is  composed  of  a  small 
amount  of  connective  tissue,  which,  just  beneath  or  outside  the 
epithelium,  sustains  collections  of  lymphoid  (or  adenoid)  tissue. 
In  the  pig,  a  considerable  quantity  of  yellow  elastic  tissue  is  found 
in  the  mucosa  outside  the  lymphoid  tissue,  but  the  amount  is 
smaller  in  man.  The  fibers  are,  for  the  most  part,  disposed  longi- 
tudinally. Many  nutrient  vessels  from  the  bronchial  artery,  cap- 
illaries, venules,  and  lymph -spaces  are  also  found  in  this  coat. 

The  muscular  coat — muscularis  mucosae — does  not  differ  from 
the  same  layer  in  other  mucous  membranes.  Its  thickness  varies 


124  STUDENTS   HISTOLOGY  * 

in  proportion  to  the  size  of  the  bronchus,  the  smaller  tubes  possess- 
ing relatively  the  thicker  walls.  The  fibers  pass  circularly,  and 
are  of  the  non- striated  or  involuntary  variety. 

The  external  coat,  or  submucosa,  is  largely  composed  of  loose 
connective  tissue,  the  fibers  being  mostly  arranged  circularly.  A 
few  delicate  elastic  fibers  run  longitudinally.  The  external  fibers, 
like  those  of  all  tubes,  ducts,  and  vessels,  are  for  the  purpose  of 
establishing  connection  with  the  organ  or  part  traversed ;  so  that 
it  is  often  difficult  to  demonstrate  the  exact  external  limit  of  a 
bronchus.  This  coat  is  liberally  supplied  with  nutrient  branches 
from  the  bronchial  artery. 

The  elasticity  and   strength  of   the  larger  and  medium -sized 


FIG.  84.    TRANSVERSE  SECTION  OF  A  PORTION  OF  HUMAN  LUNG,  SHOWING  A 
SMA.L.L  BRONCHIAL  TUBE  (X  60).     STAINED  WITH  H^EMATOXYLIN. 

A.  Lumen  of  bronchus. 

B.  Ciliated  columnar  epithelium. 

C.  Internal  fibrous  layer— mucosa. 

D.  Muscular  coat. 

E.  External  fibrous  layer— submucosa. 

F.  Pulmonary  artery. 

G.  Nerve. 

H,  H,  H.    Pulmonary  alveoli  surrounding  bronchus. 

bronchial  tubes  are  greatly  increased  by  the  presence  of  cartilage 
in  the  form  of  plates,  which  are  imbedded  in  the  external  coat. 
They  are  not  uniform  in  size,  neither  are  they  placed  regularly. 
They  frequently  overlap  one  another,  and  two  or  three  may  be 
superposed.  As  the  tubes  become  reduced  in  size  the  plates  be- 
come diminished  in  frequency — disappearing  altogether  when  a 


THE   LUNGS  125 

diameter  of  about  one  millimeter  has  been  reached.  The  cartilage  is 
of  the  hyaline  variety;  and  each  plate  is  covered  with  a  dense  fibrous 
coat,  the  perichondrium ,  which  unites  it  with  contiguous  parts. 

The  principal  bronchi  are  provided  with  a  great  number  of 
mucous  glands,  which  are  located  in  the  external  coat  or  submu- 
cosa. They  are  simple,  coiled  tubular  glands,  commencing  on  the 
inner  surface,  penetrating  the  mucosa  and  muscularis  mucosae, 
and  terminating  in  the  submucosa,  generally  within  the  cartilage, 
where  they  are  coiled  in  short,  close  turns  in  sections  resembling 
somewhat  the  larger  sweat-glands  of  the  skin.  The  ciliated  epi- 
thelium of  the  bronchial  tube  is  continued  down  the  beginning  of 
the  tube  for  a  short  distance,  after  which  the  cells  are  shortened, 
and  lose  their  cilia.  The  coiled  gland-part  of  the  tube  is  lined  with 
conical  cells,  which  are  so  large  as  to  leave  the  lumen  very  small. 
Sometimes,  and  especially  in  the  aged,  an  ampulliform  dilatation' 
of  the  tube  may  be  seen  during  its  passage  through  the  mucosa. 

The  description  just  given  will  apply  to  large  and  medium- 
sized  bronchial  tubes.  Very  important  changes  take  place  as  we 
pass  to  the  terminal  tubes. 

As  the  tubes  decrease  in  size,  the  first  coat  to  diminish  in 
thickness  is  the  outer,  or  submucosa.  We  have  already  alluded  to 
the  disappearance  of  the  cartilage,  and  the  mucous  glands  are 
lost  at  about  the  same  time.  The  outer  coat  becomes,  in  the 
small  bronchial  tubes,  so  thin  as  to  be  no  longer  distinctly  demon- 
strable. The  muscular  coat  is  the  last  to  disappear.  It  remains 
a  prominent  feature  of  the  tube  as  long  as  separate  coats  can  be 
distinguished.  The  epithelial  cells  lining  the  tubes  toward  the 
termini  become  shortened,  and,  getting  lower  and  lower,  at  last 
result  in  cuboidal  cells,  without  cilia. 

The  walls  of  terminal  bronchial  tubes  (diameter  one -fourth 
to  one -eighth  of  a  millimeter)  are  composed  of  a  slight  amount  of 
connective  tissue  in  which  an  occasional  non- striated  muscle -cell 
and  yellow  elastic  fiber  can  be  distinguished.  They  are  lined 
with  cuboidal  or  a  few  flat  cells.  No  definite  layers  are  distin- 
guishable in  these  bronchial  tubes.  In  a  transverse  section  the 
lumen  would  appear  circular. 

PRACTICAL    DEMONSTRATION 

The  histology  of  the  bronchi  can  be  studied  to  best  advantage  by  using 
tissue  from  a  freshly  killed  pig,  cat,  or  dog.  Short  pieces  of  tubes,  about  one 
•centimeter  in  diameter,  from  which  most  of  the  lung- substance  has  been  cut 


126  STUDENTS  HISTOLOGY' 

away,  should  be  hardened  quickly  in  strong  alcohol.  Transverse  sections  can 
be  made  free-hand,  or  the  tissue  may  be  infiltrated  with  paraffin  or  celloidin, 
and  cut  with  the  microtome.  Stain  with  hsematoxylin  and  eosin,  and  mount 
in  balsam. 


TRANSVERSE     SECTION    OF    PORTION    OF    BRONCHUS    OF    PIG 

(Fig.  85) 

OBSERVE  : 
(L.) 

1.  The  epithelial  lining:     (a)  The  wavy  course,     (b)  Regions 
occupied  by  beaker  or  goblet  cells.     (The  letter  E  in  the  drawing 
leads  to  such  a  group,     (c)  The  number  of  nuclei,  indicating  the 
presence  of  more  than  a  single  layer  of  cells. 

2.  The  mucosa.     (a)   Deeply  stained  blue  nuclei  of  the  lym- 
phoid  (or  adenoid)  tissue  just  beneath  the  epithelium.     (&)  Pink 
portion  of  the  region  below  the  lymphoid  tissue.     (The  longitudi- 
nal elastic  fibers  cut  transversely.)      (c)   Blood-vessels. 

3.  The  muscular  coat,     (a)  Apparent  solution  of  continuity 
in  places  caused  by  tubes  of  mucous  glands.     (&)     The  absence 
of  large  vessels  in  this  coat. 

4.  The    external    layer,     (a)    Its    extent.      (It    includes    the 
remainder  of  the  section.)      (6)   Large  cartilage  plates,  C,  stained 
blue,     (c)  Cartilage-cells.     (Note  their  differing  forms  and  dispo- 
sition in  rows  next  the  surfaces  of  the  plates.)      (d)  Perichondrium 
stained    pink.       (e)   Mucous    gland -coils.     (They    are    usually 
between   the   cartilage    and   the   muscular  coat.)      (/)   Section    of 
bronchial  arteries  and  veins,     (g)  Collections  of  adipose  tissue 
on  the  outer  surface,     (h)  Portion  or  whole  of  pulmonary  artery 
and   medullated   nerve-trunks  outside  of  and  accompanying  the 
bronchus. 

(H.) 

5.  Epithelial   lining,     (a)  Cilia   of   columnar  cells.     (6)   The 
ovoid  cells  between  the  tapering  columnar  cells,     (c)  The  "base- 
ment membrane,"  upon  which  the  columnar  cells  rest,     (d)   The 
goblet  or  beaker  cells. 

6.  The  mucosa.     (a)  The  reticulum  of  the  lymphoid  tissue. 
(It  will  appear  only  where  the  lymph -corpuscles  have  been  acci- 
dentally brushed  out.)      (&)   The  transversely  divided  ends  of  the 
elastic  fibers.     (They  appear  as  a  pink  mosaic.)      (c)  Capillaries. 
(They  may  frequently  be  traced  for  a  considerable  distance  in  their 
tortuous  course.) 


BRONCHIAL    TUBES 


127 


7.  The    cartilage    plates.       (a)     Several    cells    in    a    single 
cavity.      (&)   The  intracellular  network. 

8.  The    mucous    glands,     (a)   That    some   of    the    cells   are 


FIG.  85.     TRANSVERSE  SECTION  OF  PART  OP  THE  WALL  OP  A  LARGE  BRONCHUS. 
LUNG  OF  PIG.     STAINED  WITH  H^EMATOXYLIN  AND  EOSIN  (X60). 

E.   Epithelial  lining.    The  line  from  the  letter  leads  to  a  part  of  the 

lining  containing  large  mucous  cells  or  goblet  cells. 
I.    The  internal  fibrous  coat. 
M.  Muscular  coat. 

C.  Cartilage  plates  of  external  fibrous  coat. 

A.  Bronchial  artery.     The  pulmonary  artery  is  not  included. 

V.  Bronchial  vein. 

N.  Nerve-trunk.  < 

G.   Mucous  glands. 

D.  Obliquely  sectioned  duct. 


stained  precisely  like  the  other  mucous  or  goblet  cells,  along  the 
surface  of  the  membrane.  (5)  If  possible,  a  gland-tube  leading 
up  to  tlie  lumen  of  the  bronchus.  (An  ampulliform  dilatation 
is  shown  in  the  upper  part  of  the  drawing.) 


128  STUDENTS   HISTOLOGY 


THE   PULMONARY  BLOOD-VESSELS 

The  prominent  accompaniments  of  the  bronchus,  at  the  root  of 
the  lung,  are  the  pulmonary  artery  (carrying  venous  blood)  and 
the  pulmonary  veins. 

The  pulmonary  artery  enters  the  lung  with  the  bronchus,  fol- 
lowing its  ramifications,  to  end  in  capillary  plexuses  in  the  walls  of 
the  sac -like  dilatations,  which  are  in  connection  with  the  ultimate 
bronchial  tubes.  The  blood  is  then  collected  in  venules,  which 
unite  to  form  the  pulmonary  veins.  The  latter  pursue  an  inde- 
pendent course  in  their  exit,  not  accompanying  the  bronchial  tubes 
until  the  large  bronchial  tubes  have  been  reached. 

The  bronchial  artery  (nutrient)  enters  with  the  bronchus,  sup- 
plying its  walls  and  the  connective  tissue  framework  of  the  lung. 

A  considerable  amount  of  connective  tissue  accompanies  and 
supports  the  structures  which  enter  the  lung,  and  is  eventually  in 
connection  with  the  fibrous  framework  of  the  organ. 

The  lung  will,  therefore,  be  seen  to  differ  from  organs  gener- 
ally, in  that  it  contains  two  distinct  vascular  supplies,  viz. :  (1)  The 
pulmonary  (of  venous  blood),  entering  for  the  purpose  of  its  own 
oxygenatiou;  (2)  The  bronchial  (arterial),  which  corresponds  to 
the  usual  nutrient  blood -supply  of  organs. 

THE   PLEUEA 

The  lung  is  completely  enveloped  in  a  membrane  composed 
externally  of  endothelium,  while  the  visceral  portion  is  made  up  of 
interlacing  fibrous  and  elastic  tissue.  The  deep  or  visceral  layer 
of  the  pleura  sends  prolongations  in  the  form  of  septa  into  the 
substance  of  the  lung,  dividing  it  into  rounded  polyhedral  compart- 
ments or  lobules.  The  interlobular  septa  have  usually  become 
prominent  in  the  human  adult  from  deposits  of  inhaled  carbon  in 
their  lymph -channels. 

THE   PULMONARY  ALVEOLI 

The  lung  is  constantly  employed  in  maintaining  the  integrity 
of  the  blood.  This  is  accomplished  by  the  exposure  of  the  latter  to 
a  continual  supply  of  atmospheric  air.  The  air  is  introduced  into 
little  sacs  (termed  air-vesicles  or  alveoli),  in  the  walls  of  which  the 
blood  is  distributed  in  a  capillary  plexus.  The  air  does  not  reach 


THE   PULMONARY  ALVEOLI 


129 


the  capillaries  themselves,  inasmuch  as  they  are  covered  with  a 
layer  of  flat  cells.  These  cells,  constituting  the  parenchyma  of  the 
lung,  have  the  power,  on  the  one  hand,  of  selecting  such  material 
from  the  air  as  may  be  required,  passing  it  on  to  the  blood  in  the 
capillaries;  and,  on  the  other,  of  removing  effete  material  from  the 


FIG.  86. 


DIAGRAM  OP  AN  ULTIMATE  PULMONARY  LOBULE. 

A.  A  terminal  bronchiole. 

B.  The  air-sacs  or  alveoli. 


blood,  transferring  it  to  the  atmospheric  contents  of  the  air -sacs 
for  exhalation. 

The  air -sacs  or  alveoli  are  not  unlike  minute  bladders.  Their 
diameter  about  equals  that  of  a  terminal  bronchus;  viz.,  from  one- 
fourth  to  one -eighth,  of  a  millimeter.  A  group  of  these  alveoli  are 
associated  in  the  manner  shown  in  Fig.  86,  their  contiguous  walls 


FIG.  87.  DIAGRAM  SHOWING  AN  ULTIMATE  PULMONARY  LOBULE  IN  LONGITUDINAL 
SECTION,  SHOWING  THE  MANNER  IN  WHICH  THE  ALVEOLI  ARE  ASSOCIATED  IN 
CONNECTION  WITH  A  TERMINAL  BRONCHIOLE. 

A.  Terminal  bronchiole  entering. 

B.  The  infundibuhim. 

C.  C,  C.  Alveoli. 

fusing  and  all  opening  into  a  common  cavity,  the  infundibulum . 
The  whole  is  in  connection  with  a  terminal  bronchiole  (vide  Fig. 
87).  A  primary  lobule  having  been  thus  constructed,  several  are 
associated  and  united  to  a  slightly  larger  bronchial  twig,  and  there 
results  one  of  the  polyhedral  lobules,  previously  mentioned  as 
i 


130 


STUDENTS    HISTOLOGY 


visible,  especially  on  the  surface  of  the  lung.     By  a  repetition  of 
such  elements  the  lung  is  constructed. 

The  wall  of  a  pulmonary  alveolus  or  air -sac  is  composed  of 
connective  tissue,  supporting  the  capillary  network,  with  a  con- 
siderable amount  of  elastic  tissue.  The  whole,  as  we  have  said,  is 
lined  with  a  single  layer  of  flat,  pavement  epithelium.  The  capil- 
lary plexus,  when  filled  with  blood,  affords  the  most  prominent 
feature  of  the  wall ;  but  when  the  vessels  have  been  emptied  of 
their  contents,  tHey  become  very  insignificant  under  the  micro- 


FIG.  88.     TRANSVERSE  SECTION  OF  A  SINGLE   PULMONARY  ALVEOLUS.     CAPILLARIES 
INJECTED.     STAINED  WITH  H^MATOLYLIN  AND  EOSIN  (X400). 

A,  A,  A.  Walls  of  the  alveolus. 

B,  B.  Injected  capillaries. 

C,  C.  Pavement  cells  lining  the  alveolus.    These  cells  cover  the  capillaries,  but  do  not  so 
appear  in  the  drawing,  as  the  latter  are  filled  with  an  opaque  injection.     The  observer  is  sup- 
posed to  he  above  the  sectioned  alveolus,  viewing  the  cup-shaped  cavity. 

scope,  and  the  fibro- elastic  tissue  becomes  more  apparent.  You 
will  have  observed  that,  aside  from  the  vascular  supply,  the  his- 
tology of  an  alveolar  wall  resembles  very  closely  that  of  a  terminal 
bronchiole,  and  when  the  vessels  are  all  empty  it  is  frequently  diffi- 
cult to  differentiate  them  in  the  mounted  section. 


THE   LUNGS  131 

Fig.  88  shows  a  single  alveolus,  the  vessels  of  which  have  been 
injected  with  a  solution  of  colored  gelatin.  The  alveolus  has  been 
divided  through  the  middle,  and  shows  as  a  cup -shaped  cavity. 
The  fibrous  marginal  walls  are  indicated,  with  their  tortuoua_ 
capillaries.  The  epithelial  cells  lining  the  bottom  are  obscured  by 
the  opaque  capillaries,  and  shown  only  between  the  loops.  It  is 
probable  that  these  cells  cover  the  plexus  completely,  as  they  line 
the  alveoli. 

We  now  encounter  an  obstacle  which  will  frequently  be  met  in 
our  study  of  organs.  It  consists  of  the  difficulty  in  recognizing  in 
sections  the  plan  of  structure  which  we  have  learned  is  peculiar  to 
the  organ  under  consideration.  For  example:  A  lung  has  been 
compared  to  a  tree.  The  bronchi  are  the  representatives  of  the 
branches,  and  the  air -sacs  of  the  fruit.  Well,  we  make  a  section 
from  human  lung — it  matters  little  as  to  the  direction — with  every 
possible  care,  and  the  image  in  the  field  of  the  microscope  resem- 
bles a  fragment  of  ragged  lace  more  nearly  than  anything  else! 
The  arrangement  of  the  tubes  and  alveoli  of  the  lung  has  been 
determined  by  filling  the  cavities  with  melted  wax,  which,  when 
cold,  and  the  tissue  destroyed  by  acid,  gives  a  perfect  mould  of  the 
organ.  A  section  gives  us  but  a  single  plane,  and  this  fact  must  be 
always  borne  in  mind. 

PRACTICAL     DEMONSTRATION 

With  a  very  sharp  razor,  cut  centimeter  cubes  from  pig's  lung.  Select 
portions  free  from  large  bronchi,  with  the  pleura  on  one  side  at  least,  and 
harden  with  strong  alcohol.  Human  lung,  as  fresh  as  possible,  may  be  treated 
in  the  same  manner.  The  epithelium  of  the  alveoli  shows  best  in  young  lung. 
Lung  must  be  made  very  hard,  or  thin  sections  cannot  be  cut.  If  the  ordinary 
ninety-five  per  cent,  alcohol  does  not  harden  sufficiently,  the  process  may  be 
completed  by  transferring  the  tissue  for  twenty-four  hours  to  absolute  alcohol. 
The  celloidin  process  is  well  adapted  to  this  structure. 

Stain  the  sections  with  borax -carmine,  or  hsematoxylin  and  eosin.  Mount 
in  balsam. 


SECTION    OF    LUNG    OF    PIG    (Vide  Fig.  89) 

OBSERVE  : 
(L.) 

1.  The  large  scalloped   openings,  A,  A,  transversely  divided 
infundibula. 

2.  The  divided  alveoli,  B,  B,  so  sectioned  as  to  cut  off  both 


132 


STUDENTS   HISTOLOGY 


bottom  and   top,   and   show   no    epithelial    lining   excepting   at 
inner  edge  of  periphery. 

3.  The  alveoli,  C,  C,  divided  so  as  to  show  a  cup- shaped  bot- 
tom or  top.     (The  minute  granules  are  the  nuclei  of  the  lining 
cells.) 

4.  The  alveoli,  D,  D,   so  cut  as  to  leave  most  of  bottom  or 
top,  showing  an  opening  in  the  center  where  the  sac  has  been 
sliced  off. 


FIG.    89.     SECTION   OF    LUNG  OF   PIG.      STAINED   WITH   H^EMATOXYLIN   AND 

EOSIN    (X60). 

A,  A.  Infundibula  in  T.  S. 

B,  B,  B.  Alveoli;  so  sectioned  as  to  show  the  outline  only. 

C,  C,  C.  Alveoli;  so  sectioned  as  to  present  cup-shaped  cavities. 

D,  D,  D.  Alveoli;  so  sectioned  as  to  divide  the  top  (or  bottom). 

E,  E.  Terminal  bronchioles  in  T.  S. 


5.  Openings,  E,  E,  which  are  about  the  same  size  and  bear  a 
general  resemblance  to  those  of  Obs.  2.  (Note  that  their  internal 
edges  are  smooth  and  not  ragged.  They  are  terminal  bronchi- 
oles. No  larger  bronchial  tubes  have  been  included  in  the 
section.) 


\ 


HUMAN  LUNG  133 

HUMAN    LUNG — SECTION    SHOWING    A    SINGLE 
ALVEOLUS    (Fig.  90) 

OBSERVE  : 
(L.) 

1.  The  outline  of  alveolus.  (The  alveoli  in  human  lung  will 
show  much  distortion,  as  the  tissue  cannot  be  secured  in  perfect 
condition.) 


FIG.   90.     TRANSVERSE  SECTION  OF  A  SINGLE  PULMONARY  ALVEOLUS.     STAINED 
WITH  H^EMATOXYLIN  (X  400). 

A.  A,  A.   Walls  of  alveolus. 

B.  Lumen. 

C.  C,  C.   Capillaries  variously  sectioned  in  their  tortuous  course. 

D.  Pavement  epithelial  cells  intact. 

E.  Detached  pavement  cell. 

F.  Detached  cluster  of  pavement  cells. 
F'.  Granular  lining  cells. 

G.  Pulmonary  artery. 

(H.) 

2.  The  fibrous  wall,  A,  A. 

3.  The  lumen,  B.     (The  bottom  or  top  has  been  cut  off  in 
making  the  section.) 

4.  The  tortuous  capillaries,  C,  C,  in  the  fibrous  wall. 


134  STUDENTS   HISTOLOGY 

5  The  lining  epithelial  cells,  (a)  Those  remaining  attached 
to  the  edges  of  the  wall,  D.  (&)  Detached  cells.  E.  (c)  Groups 
partly  detached,  F,  F. 

6.  The  divided  pulmonary  artery,  G.  (A  medium  -  sized  bron- 
chial tube  existed  in  the  section  immediately  to  the  left  of  the 
artery.) 

FCETAL     LUNG 

Harden  the  lung  of  a  foetus,  preferably  human,  in  Miiller's  or  Orth's 
fluid.  After  washing,  finish  hardening  in  alcohol  ;  imbed  in  celloidin;  cut; 
stain  with  haematoxylin  and  eosin;  mount  in  balsam. 

Observe  the  polyhedral  form  of  the  epithelial  cells  lining  the 
alveoli.  A  few  such  polyhedral  cells  can  be  demonstrated  in  the 
alveoli  of  the  adult  lung  with  silver  staining,  and  they  correspond 
to  the  polyhedral  cells  of  the  terminal  bronchioles.  It  appears 
that  the  plate -like  cells  lining  the  alveoli  of  the  adult  lung  are 
derived  from  the  polyhedral  cells  of  the  foetal  lung,  which  become 
flattened  from  the  distension  which  they  undergo  when  the  alveoli 
are  inflated. 


THE    TEETH  135 


THE    TEETH 

A  human  tooth  is  a  calcareous  structure  of  extreme  hardness, 
and  is  divided  into  an  exposed  crown,  a  constricted  neck,  and  one 
or  more  concealed  roots — the  latter  being  inserted  into  an  alveolus, 
by  means  of  which  the  whole  is  very  firmly  connected  with  the 
maxillary  bone. 

The  central  portion  presents  an  elongated  cavity  (pulp -cham- 
ber) containing  vascular,  nervous,  and  connective  tissue  elements — 
the  pulp. 

The  pulp -cavity  is  surrounded  by  the  dentine,  which  consti- 
tutes the  major  portion  of  the  tooth 

The  crown  portion  of  the  dentine  is  provided  with  a  covering 
of  enamel,  while  the  root  is  invested  with  an  osseous  cementum, 
or  crusta  petrosa. 

A  thin  membrane,  1  /*  or  less  in  thickness — called  the  membrane 
of  Nasmyth  or  the  cuticula — covers  the  enamel  in  early  life,  while 
the  cementum  receives  a  periosteal  investiture.  The  vascular  and 
nervous  elements  of  the  pulp  obtain  admission  to  the  pulp -cavity 
by  a  perforation  or  foramen  at  the  apex  of  the  root. 

The  Pulp. — The  ground -substance,  or  stroma  of  the  pulp,  is  a 
form  of  primitive  connective  tissue,  gelatinous  rather  than  mark- 
edly fibrous.  It  contains  elongated  capillary  loops,  multipolar 
cells,  and  medullated  and  non-medullated  terminal  nerve -fibrils. 

Surrounding  the  pulp  mass,  and  next  to  the  dentinal  wall  of 
the  chamber,  we  find  a  single  layer  of  elongated  cells— odontoblasts. 
These  are  probably  in  communication,  by  means  of  processes  or 
prolongations,  with  fibrous  elements  of  the  pulp. 

Dentine. — The  dentinal  stroma  or  matrix  is  made  of  fibrous 
tissue  containing  calcium  salts,  and  is,  next  to  the  enamel,  the 
hardest  tissue  of  the  body.  The  matrix  is  pierced  with  the  denti- 
nal canals  (extremely  minute  channels,  only  5/*  in  diameter), 
which  radiate  from  their  beginning,  next  the  pulp -chamber, 
toward  the  outer  portion  of  the  dentine.  These  canals  branch 
and  anastomose,  and  are  lined  with  an  exceedingly  thin  den- 
tinal sheath. 

From  the  outer  extremity  of  the  odontoblasts  of  the  pulp  nu- 
merous prolongations  are  sent  which  are  probably  continued  within 
the  dentinal  canals  as  the  dentinal  fibers.  The  dentinal  canals 
terminate  exteriorly,  by  very  fine  lumina,  in  a  system  of  irregu- 


136 


STUDENTS   HISTOLOGY 


FIG.  91. 


DIAGRAM  OF  THE   STRUCTURE  AND  IMPLANTATION  OF  A  NORMAL- 
INCISOR  TOOTH.     (BODECKER.) 


L.    Cuticle  of  enamel,  Nasmyth's  membrane. 

E.    Enamel. 

D.    Dentine  with  uniformly  distributed  canaliculi. 

I.     Interzonal  layer  between  enamel  and  dentine. 

B.    Border-line  between  enamel  and  cementum  of  neck. 

S.    Cementum  of  neck. 

Ce.  Cementum  of  root. 

Z.    Interzonal  layer  between  dentine  and  cementum. 

P.    Pericementum. 

A.    Arteriole  of  pulp,  branching  into  capillaries. 

V.    Vein  of  pulp  taking  up  capillaries. 

N.    Medullated  nerve-fibers  of  pulp. 

Eg.  Stratified  epithelium  of  gum.  Pg.  Papillary  layer  of  gum. 

Pe.  Periosteum.  Co.  Cortical  bone  of  alveolus  or  socket. 

Ca.   Cancellous  bone-tissue  of  alveolus.     M.    Medullary  spaces  of  cancellous  bone. 


THE    TEETH  137 

larly  formed  openings,  interglobular  spaces,  which  are  channeled 
in  the  outer  part  of  the  dentine.  The  dentinal  terminal  fibers  are 
in  connection  with  branched  cells  which  occupy  the  interglobular 
spaces. 

The  Enamel. — The  part  of  the  dentine  above  the  neck  of  the 
tooth  is  protected  by  a  covering  of  enamel.  The  enamel  consists 
of  prisms,  4  p  in  diameter,  united  into  bundles  by  a  little  cement 
substance,  which  pass  in  a  direction  nearly  at  a  right  angle  to 
the  surface  of  the  dentine.  They  are  of  extreme  density,  contain 
little  besides  inorganic  material,  and  in  a  vertical  section  the  whole 
is  traversed  by  parallel  striae,  not  unlike  the  markings  indicating 
tree -growth — the  lines  of  Retzius. 

Cementum.— The  fang  portion  of  the  dentine  is  invested  with  a 
thin  layer  of  true  bone,  containing  lacunce  and  canaliculi,  but  no 
Haversian  canals.  The  cementum  is  provided  with  pericementum 
(periosteum),  which  forms  the  bond  of  union  between  the  teeth 
and  the  process  of  the  maxillary  bone.  The  bone- corpuscles  are  in 
connection,  through  the  canaliculi,  with  the  cells  in  the  interglo- 
bular spaces  of  the  dentine.  It  will  be  seen  that  the  connective 
tissue  elements,  at  least  of  the  pulp,  are  in  eventual  histological 
connection  with  the  bone -corpuscles  of  the  cementum. 


PRACTICAL     DEMONSTRATION 

The  illustrations  given  in  text-books  have  been  drawn  from  dried  teeth, 
ground  down  to  the  requisite  thinness  by  means  of  corundum  or  emery  wheels. 
This  is  a  very  tedious  process,  and  is  impracticable  with  the  student.  If  such 
specimens  are  desired,  it  will  be  advisable  to  purchase  them  already  mounted. 
They  only  give  the  skeleton  of  the  organ,  all  the  soft  tissues  being  destroyed 
by  the  drying  and  grinding. 

,  While  dry  specimens  exhibit  the  plan  of  a  tooth,  the  soft  tissues  must  be 
studied  in  sections  made  after  the  inorganic  constituents  have  been  removed. 
Teeth  immediately  after  extraction  are  to  be  treated  in  the  same  manner  as 
described  for  bone.  A  one-sixth  per  cent,  chromic-acid  solution,  to  which  five 
drops  of  nitric  or  hydrochloric  acid  have  been  added,  may  be  used.  Let  the 
quantity  of  liquid  be  liberal,  and  from  time  to  time,  say  every  three  days,  add 
a  few  drops  of  the  nitric  acid.  The  decalcification  should  proceed  slowly,  and 
may  be  complete  in  from  two  to  three  or  four  weeks.  The  earthy  matters 
will  first  be  dissolved  from  the  surface.  Watch  the  action  carefully,  ascer- 
taining the  progress  of  decalcification  by  pricking  a  fang  with  a  needle.  If 
the  acid  be  too  strong,  and  the  action  too  rapid,  the  whole  may  be  destroyed. 
When  the  decalcification  is  complete,  a  needle  may  be  easily  passed  through 
the  tooth,  and  sections  may  be  made  with  the  razor  or  knife,  with  or  without 
a  microtome.  The  form  will  be  preserved  except  as  regards  the  enamel;  this 


138  STUDENTS   HISTOLOGY 

will  be   entirely  dissolved.       The    enamel    prisms    may    be    demonstrated    by 
treating  broken  fragments  with  dilute  acid  for  a  short  time  only. 

Sections  should  be  stained  with  carmine  and  picric  acid  and  mounted  in 
glycerin.  For  the  study  of  the  development  of  teeth,  foetal  jaws  may  be 
treated  as  just  described;  and,  when  properly  decalcified  and  hardened,  should 
be  infiltrated  with  celloidin,  sectioned,  and  stained. 


TRANSVERSE     SECTION    OP    FANG    OF    HUMAN     DECIDUOUS    CANINE 
TOOTH— DECALCIFIED      (Fig.  92) 

OBSERVE  : 
(L.) 

1.  Division     into     pulp,    dentine,    cementum,    and     perice- 
mentum. 

2.  Line  of  junction  of  pulp  and  dentine.     (If  the  elements  of 
the  pulp  are  intact,  note  the  layer  of  deeply  stained  odontoblasts 
next  the  dentine.) 

3.  External  limit  of  dentine.      (Note  here  the  deeply  stained 
granular  line  of  Purkinje.     This  is  the  location  of  the  interglobu- 
lar  spaces.     The  deep  color  is  due  to  the  staining  of  the  contents 
of  their  cells.) 

4.  The  striae  of  the  dentine.     (The  dentinal  canals  and  stained 
contents.) 

5.  The  laminated  cementum.     (The    yellowish    pink  dots  on 
the  lacunas.) 

(H.) 

6.  Elements   of   the   pulp,     (a)   The   layer  of   odontoblasts. 
(Note  their  internal  processes  connecting  with  other  cells  of  the 
pulp;     and   the    external   processes    passing    into    the    dentinal 
canals.)     (6)  The    sparsely    fibrillated    character    of    the    pulp- 
tissue,     (c)   Sections  of   vascular   loops.      (The  nerve-elements 
may  be  demonstrated,  particularly  if  the  section  be  made  near  the 
apex  of  the  root,  where  the  fibers  are  medullated.      The  terminal 
fibrillae  are  non- medullated.) 

7.  Dentinal    elements.      («)  The    dentinal    canals.     (&)  The 
dentinal   sheath.     (Better  demonstrated  in  transverse   sections.) 
(c)  Dentinal  fibers.     (In  transverse   sections  the  canals   are  well 
shown  lined  with  a  membrane  of  extraordinary  tenuity,  with  the 
fiber  appearing  as  a  central  dot.)     (d)  Fine  dentinal  fibers  near 
the  outer  limit,     (e)  Interglobular   spaces.     (An   occasional  cell 
may  be  made  out  in  the  larger  spaces.     They  were  formerly  sup- 


THE   TEETH 


139 


posed  to  contain  a  gelatinous  material  only.     Note  the  connection 
between  these  spaces  and  the  termini  of  the  dentinal  fibers.) 

8.  The  cementum.     (a)  The  lacunae.      (&)   Bone-corpuscles 
in  the  last.     (The  canaliculi  are  not  well  demonstrated  here,  as  the 
tissue  is  very  translucent  and  feebly  stained.     These  minute  canals 
are  better  indicated  in  dried  bone.) 

9.  The  pericementum.     (Note  its  dense  fibrillar  meshwork.) 


FIG.  92.    TRANSVERSE   SECTION  OF  FANG  OF  A  HUMAN  DECIDUOUS   CANINE  TOOTH, 
DECALCIFIED    WITH    CHROMIC    AND    NITRIC    ACIDS   AND   STAINED   WITH   PICRO- 

CARMINE    (X  400). 

A,  B.  Line  through  the  dentine  indicating  the  point  at  which  the  edges  have  been  made  to 
join  after  the  omission  of  an  intervening  portion.  This  was  necessary  in  order  that  the  dif- 
ferent layers  might  be  shown  in  a  single  drawing. 

C,  D.    Junction  line  between  the  pulp  and  dentine. 

E,  F.    Junction  line  between  dentine  and  cementum. 

G,  G.    Odontoblasts  of  the  pulp. 

H,  H.   Stellate  connective  tissue  cells  of  the  pulp. 

I,  I.      Dentinal  processes  of  odontoblasts. 

J,  J.      Dentinal  fibers. 

K,  K.    Terminal  branching  dentinal  fibers. 

L,  L.    Interglobular  spaces  of  dentine. 

M,  M.  Lacunae  of  the  cementum.  The  drawing  does  not  show  the  periosteal  investiture 
of  the  crusta. 


140  STUDENTS  HISTOLOGY 


GLANDS 

A  gland  is  an  organ — frequently  subsidiary  to  and  located 
within  other  organs — whose  cells  manufacture  from  the  blood  pro- 
ducts to  be  utilized  in  the  performance  of  some  of  the  functions  of 
the  body,  or  waste  products  which  are  to  be  excreted. 

Simple  glands  are  tubes  or  cavities,  with  connective  tissue  walls 
lined  with  epithelial  cells,  which  are  usually  placed  upon  a  base- 
ment membrane.  Around,  and  in  close  proximity  to  the  lining, 
is  spread  a  plexus  of  blood -capillaries.  In  compound  glands,  the 
simple  glands  (acini  or  alveoli)  are  enclosed  by  connective  tissue 
in  groups  called  lobules,  and  larger  groups  called  lobes.  The 
same  connective  tissue  is  continued  to  form  a  capsule  over  the 
outside. 

The  essential  parts  of  a  gland  are,  therefore: 

1.  A  duct,  or  efferent  conduit  for  the  secretion. 

2.  Parenchyma,  or  cells  engaged  in  secretion. 

3.  A  blood -vascular  supply. 


TUBULAR    GLANDS 

The  simplest  gland-structure  is  offered  in  the  form  of  a  tube. 
Glands  are,  frequently,  little  more  than  tubular  depressions  in 
mucous  surfaces.  Examples  are  found  in  the  uterus,  and  small 
and  large  intestines. 

COILED    TUBULAR    GLANDS 

Tubular  glands  are  often  greatly  elongated,  with  the  blind 
extremity  coiled.  This  variation  presents  the  simplest  differentia- 
tion between  the  part  of  the  tube  which  is  secretory,  and  the  duct, 
or  drainage  part.  With  this  change  in  function  of  the  different 
extremities  of  the  tube  will  occur  a  change  of  epithelium.  The 
cells  belonging  to  the  duct-end  will  usually  retain  the  columnar 
form;  while  the  actively  secreting  elements  will  become  enlarged, 
more  nearly  filling  the  tube,  and  assume  a  polyhedral  form  from 
pressure. 

Examples  have  already  been  seen  in  the  sweat-glands  of  the 
skin. 


SIMPLE   AND    COILED    TUBULAR    GLANDS 


141 


FIG.  93.     DIAGRAM.     SIMPLE  TUBULAR  GLAND, 

A.  Lining  cells— parenchyma. 

B.  Capillary  plexus,  supplying  the  parenchyma, 
0.    Connective  tissue  supporting  capillaries. 

D.   Arterial  supply. 


FIG.  94.     DIAGRAM.     COILED  TUBULAR  GLAND. 
Same  references  as  Fig.  93. 


142 


STUDENTS   HISTOLOGY 


FIG.  95.     DIAGRAM.    BRANCHED  TUBULAR  GLAND. 
References  same  as  Fig.  93. 


FIG.  96.     DIAGRAM.     ILLUSTRATING  THE  PLAN  OF  ACINOUS  GLANDS, 
References  same  as  Fig.  93. 


GLANDS  143 


BRANCHED  TUBULAR  GLANDS 

With  the  branching  of  the  duct-portions  of  gland-tubules, 
usually  occurs  a  dilatation  of  the  extremities  into  acini  or  alveoli, 
although  pure  examples  of  branched  tubular  glands  are  afforded  in 
the  gastric  and  uterine  glands. 

The  most  nearly  typical  branching  of  gland -like  tubules  is 
afforded  by  the  tubuli  uriniferi  of  the  kidney,  or  the  system  of 
tubes  in  the  testicle.  The  tubules  here  present  other  features 
peculiar  to  them,  which  will  be  referred  to  under  the  proper  head. 


ACINOUS    GLANDS 

The  dilatation  of  branching  tubules,  referred  to  under  the 
previous  heading,  results  in  the  formation  of  acinous  glands. 
They  are  formed  by  the  subdivision  of  a  main  tube  or  duct,  with 
repeated  branching  of  the  secondary  tubules.  Collections  of  ter- 
minal branches  often  result  in  globular  masses,  which  are  more 
or  less  perfectly  isolated  from  one  another  by  connective  tissue. 
In  this  way  compound  acini  are  produced,  such  as  the  pancreas, 
the  salivary,  mammary,  and  buccal  glands. 

The  large  compound  acinous  glands  are  also  called  compound 
racemose  glands.  Simple  acinous  glands  do  not  occur  in  human 
tissues. 

THE    PAROTID    GLAND 

The  parotid,  submaxillary ,  sublingtial,3ind.  bitccal  salivary  glands 
are  typical  glandular  structures,  with  individual  peculiarities  only 
in  respect  to  the  cell-elements  ;  these  vary  according  to  the  nature 
of  the  secretion  formed  in  each. 

The  parotid  is  a  compound  acinous  gland,  leading  from  which 
is  a  principal  duct — lined  with  tall  columnar  cells — which  collects 
the  fluid  saliva  from  the  different  divisions  of  the  organ. 

As  the  duct  penetrates  the  gland  it  branches  freely,  the  lumina 
becoming  smaller  and  the  cells  shorter  as  thQ  deeper  parts  are 
approached. 

Each  terminal  duct  is  in  connection  with  several  acini.  The 
connective  tissue  adventitia  of  the  duct  becomes  the  thin  wall  of 
the  acinus,  and  the  lining  cells  broaden,  frequently  become  poly- 


144 


STUDENTS   HISTOLOGY 


FIG.   97.     SECTION  OF  A  SMALL  PORTION  OP  THE  PAROTID  GLAND.     STAINED  WITH 
H^EMATOXYLIN  AND  EOSIN   (X  250). 

A.  Narrowing  of  the  duct  from  a  small  lobule,  before  entering  a  larger  duct. 

B.  Dilatation  of  a  duct  after  leaving  a  small  lobule. 

C.  Primary  lobules,  in  nearly  L.  S. 

D.  Acini  in  T.  S.,  showing  the  minute  lumen. 

E.  Connective  tissue  supporting  the  gland. 

F.  Striated  muscular  fiber  adjacent  to  the  gland. 

G.  Adipose  tissue  in  the  loose  areolar  tissue. 

hedral,  and  are  bluntly  pointed.     The  cells  so  nearly  fill  the  acini 
as  to  leave  a  small  and  not  easily  recognized  lumen. 
The  gland  is  richly  supplied  with  blood-vessels. 


THE   SUBMAXILLARY    GLAND 

The  submaxillary  is  presented  as  an  example  of  a  typical  mixed 
gland.  The  general  arrangement  is  not  unlike  that  of  the  other 
salivary  glands.  Its  peculiarity  appears  in  the  parenchyma,  and 
will  be  noticed  later. 

Pure  mucous  glands  are  found  in  the  submucosa  of  the  mouth, 
tongue,  fauces,  trachea,  and  the  larger  bronchi. 


GLANDS 


145 


FIG.  98.     SECTION  OF  PART  OF  THE  SUBMAXILLARY  GLAND  (X  250). 

A.  Narrow  duet  from  terminal  lobules. 

B.  Small  duct  in  T.  S. 

C.  Small  duct  in  oblique  section. 

D.  Transversely  divided  acini,  showing  large  lumen. 

E.  Mucus    remaining  in  the  lumina. 

F.  Striated  muscular  fibers. 

G.  Adipose  tissue. 

THE   PANCREAS 

The  histology  of  the  pancreas  is,  in  general,  that  of  a  true 
serous  gland,  like  the  parotid.  It  has  been  called  by  physiolo- 
gists the  abdominal  salivary  gland. 

The  lobules  are  more  tubular  and  less  regular  in  size  and 
form;  and  the  lumen  of  the  acini  is  much  less  easy  of  demon- 
stration, in  an  ordinary  hardened  section,  than  the  same  in  the 
parotid. 

The  branches  of  the  pancreatic  duct  are  provided  with  a  very 
thick  adventitia,  are  lined  with  short  columnar  cells,  and  seldom 
present  the  dilatation  which  generally  occurs  in  a  serous  gland  on 
entering  the  lobule. 


146 


STUDENTS   HISTOLOGY 


PAROTID   AND   SUBMAXILLARY   GLANDS,    AND   THE   PANCREAS 
Practical   Demonstration 

The  tissue  must  be  fresh,  divided  in  small  pieces— not  larger  than  a  centi- 
meter cube — and  hardened  by  placing  in  ninety-five  per  cent,  alcohol  for  twelve 
hours,  after  which  fresh  spirit  should  be  substituted.  If,  after  the  lapse  of 
another  twelve  hours,  the  tissue  should  not  be  sufficiently  firm,  it  should  be 
placed  in  a  small  quantity  of  absolute  alcohol  for  three  hours.  Sections  should 


Fia.  99.    SECTION  FROM  THE  PANCREAS. 

A.  Wall  of  a  large  duct. 

B.  The  somewhat  cubical  lining  cells. 

C.  Arteries. 

D.  Lumen  of  the  acini,  T.  S. 

E.  Terminal  duct  leaving  a  lobule. 

F.  Acini  in  L.  S. 

be  made  immediately  after  hardening — as  more  prolonged  action  of  the  strong 
spirit  will  cause  the  tissue  to  contract. 

Sections  may  be  cut  with  or  without  a  simple  microtome — the  desideratum 
being  thin  rather  than  large  cuts. 

Stain  lightly  with  haematoxylin  and  deeply  with  eosin. 

After   sections  of   hardened    tissue    have   been    examined,   the    glandular 


GLANDS  147 

parenchyma  may  be  profitably  studied  in  teasings  from  tissue  which  has  been 
in  Miiller  twenty-four  hours.  Wash  the  teasings  on  the  slide  with  a  liberal 
supply  of  water,  removing  the  same  from  time  to  time  with  blotting-paper. 
Add  a  drop  of  haematoxylin  solution ;  and,  after  washing  this  away,  add  a  drop 
of  glycerin,  and  cover.  This  method  is  very  generally  useful  for  teased  m* 
scraped  fragments  of  glandular  structures. 


! 


(Figs.  97,  98  and  99) 

OBSERVE: 
(L.) 

1.  The    connective    tissue.       (Most  abundant    in   the  parotid 
gland,  and  least  so  in  the  pancreas.) 

2.  The  ducts.     (Note  the  flattening  of    the  lining  columnar 
cells,  as  the  ducts  approach  the  acini,  until  mere  scales  result. 
Also  the  thick  connective  tissue  adventitia,  especially  demonstrable 
in  the  pancreas.) 

3.  The  lobules.     (These  are  formed  by  several  acini,  and  are* 
most  typical  in  the  parotid.     It  must  be  remembered  that  only  one 
plane  is  visible,  and  that  there  is  little  perspective.) 

4.  The  acini.     (Note  the  lumina — large  in  the  submaxillary, 
less  so  in  the  parotid,  and  least,  and  often  difficult  to  make  out, 
in  the  pancreas. 

5.  The  blood-vessels,   muscular   and   adipose    tissue.     (The 
two  latter  are  demonstrable  only  in  the  salivary  glands,  and  do  not 
belong  properly  to  the  gland  itself.     The  capsule  of  the  pancreas, 
in  common  with  such  structures  in  general,  contains  adipose  tissue. 
The    abundant   interacinous    capillary   plexuses    of    the    pancreas 
require  the  high -power  for  satisfactory  demonstration.) 

(H.) 

6.  The  parenchyma.      («)  The   small  but  distinct  shortened 
columnar  cells  of  the  acini  of  the  parotid.     (Observe  that  they 
are  frequently  so  formed  that  the  convexity  of  one  cell  fits  into  the 
concavity  of  its  neighbor.     Where  seen  in  transverse  section,  the 
outline  is  a  polygon.     Note  especially  the  change  in  the  parenchy- 
matous  elements  as  the  terminal  duct  merges  into  an  acinus.) 

(6)  The  large,  swollen  cells  of  the  mucous  acini — submaxil- 
Im-y.  (Observe  the  comparative  clearness  of  the  cells.  They 
contain  a  very  delicate  reticulum,  and  their  nuclei  are  often 
obscured  and  frequently  seen  to  be  placed  at  the  junction  of  the 
cells.) 

(c)  The   rounded,   often    polyhedral    cells    of    the   pancreas. 


148  STUDENTS    HISTOLOGY 

(They  resemble  the  parotid  elements,  although  smaller  and  less 
granular.  The  acini  are  more  tubular  than  in  the  parotid  gland. 
Even  with  the  low-power  one  may  distinguish  small,  rounded  areas 
called  the  bodies  of  Langerhans.  They  are  probably  groups  of 
immature  acini.) 

(<Z)  In  the  smaller  ducts  of  the  parotid  and  submaxillary  glands, 
notice  that  the  lining  epithelial  cells  have  vertical  striations  at  the 
outer  border. 

The  sublingual  gland  in  man  is  an  almost  purely  mucous 
gland.  The  parotid  is  purely  serous,  and  has  a  secretion  of  that 
character.  It  is  reckoned  as  a  true  salivary  gland.  The  submax- 
illary, having  elements  of  both  kinds,  is  called  mixed.  In  the 
serous  glands,  when  the  cells  are  filled  with  secretion,  they  appeal- 
large,  with  fine  granules.  After  discharge  of  the  secretion  they  are 
smaller,  dark,  and  granular.  The  cells  of  the  mucous  glands  may 
be  found  large  and  clear,  or  after  discharge  of  the  mucus,  also 
smaller,  dark,  and  granular.  At  the  borders  of  the  acini  of  the 
mucous  glands  there  may  be  seen  crescent -shaped  groups  of  granu- 
lar cells,  the  demilunes  .of  Heidenhain. 


TEE    THYROID    GLAND 

The  thyroid  gland  is  a  compound  tubular  gland.  The  tubular 
acini  are  40  to  120  p-  in  diameter.  Loose  connective  tissue  unites 
them  into  lobules  and  lobes,  and  forms  a  covering  for  the  whole. 
The  acini  are  closed  cavities.  They  are  lined  by  low  columnar  or 
cubical  epithelial  cells.  The  cells  are  limited  by  a  basement  mem- 
brane. The  acini  are  usually  filled  with  homogenous,  yellow, 
translucent  material,  called  the  colloid  substance,  which  is  formed 
by  the  epithelial  cells.  The  blood  supply  is  abundant,  and  a  rich 
•capillary  network  surrounds  the  acini. 

The  lymphatic  network  is  also  profuse,  and  the  characteristic 
colloid  substance  may  be  found  within  the  lymphatics.  Nerve- 
fibers  are  not  numerous.  They  are  mostly  non-medullated,  derived 
from  the  sympathetic.  Although  the  thyroid  gland  of  the  adult 
has  no  duct,  in  the  embryo  it  has  one — the  thy ro- glossal  duct, 
which  has  an  opening  corresponding  to  the  foramen  caecum,  near 
the -base  of  the  tongue.  Later  on,  this  duct  becomes  obliterated 
.for  the  most  part. 


THE   MOUTH   AND    PHARYNX  149 


THE    MOUTH   AND    PHARYNX 

The  mottth  cavity  is  lined  by  a  mucous  membrane,  consisting^ 
of  a  stratified  squamous  epithelium  and  a  connective  tissue  layer 
below  it.     The  connective  tissue  layer  possesses  minute  papillae 
resembling   those  of   the   skin.      Numerous  mucous   glands   open 
into  the  oral  cavity,  as  well  as  the  salivary  glands. 

The  tongue,  which  is  composed  chiefly  of  striated  muscle,  ex- 
hibits on  its  upper  surface  very  large  papillae.  These  papillaa  are 
of  three  sorts:  (1)  Filiform,  or  conical;  (2)  fungiform,  or  those 
having  a  constricted  base,  and  (3)  circumvallate,  which  are  only 
eight  or  ten  in  number,  arranged  like  an  inverted  V,  at  the  back 
of  the  tongue.  The  last  variety  are  large,  fungiform,  and  sur- 
rounded by  a  depression,  outside  of  which  is  a  wall -like  elevation. 
Taste -buds  are  flask -shaped  collections  of  epithelial  cells,  special- 
ized for  the  perception  of  taste,  and  supposed  to  be  connected  with 
nerve-fibers.  .They  occur  at  the  sides  of  the  circumvallate  papillae 
and  elsewhere  on  the  tongue.  They  are  most  easily  studied  in 
sections  of  the  papillae  foliata?  of  the  rabbit,  wrhich  are  symmetrical, 
oval  areas,  marked  with  parallel  ridges,  at  the  back  of  the  tongue. 
There  is  an  abundance  of  lymphoid  tissue  at  the  back  of  the  tongue, 
either  diffused  or  occurring  as  distinct  spherical  lymph -follicles. 

The  tonsils  are  large  collections  of  lymphoid  tissue,  containing 
numerous  denser  spherical  masses,  lympli- follicles.  Stratified  squa- 
mous epithelium  covers  the  free  surface  of  the  tonsils  and  lines 
certain  blind  depressions  into  the  tonsils  (crypts).  The  epithelium 
is  more  or  less  infiltrated  with  lymphoid  cells,  which  enter  it  from 
the  underlying  tissue.  The  attached  surface  of  the  tonsil  is  covered 
by  a  connective  tissue  capsule,  which  forms  an  adventitia. 

The  so-called  salivary  corpuscles  are  lymphoid  cells  which  have 
escaped  and  become  mixed  with  the  saliva. 

The  structure  of  the  pharynx  is  nearly  like  that  of  the  mouth. 
Only  the  lower  division,  however,  is  lined  with  stratified  squamous 
epithelium.  The  portion  above  the  level  of  the  soft  palate  is  cov- 
ered with  stratified  columnar  epithelium,  which  is  also  ciliated, 
indicating  its  connection  with  the  respiratory  tract.  The  mucous 
membrane  of  the  pharynx  also  contains  mucous  glands  and  lym- 
phoid tissue.  A  mass  of  lymphoid  tissue  occupying  a  position  in 
the  upper  part  between  the  Eustachian  tubes  is  called  the  pharyn- 
geal  tonsil  of  Luschka. 


150  STUDENTS  HISTOLOGY 


THE  (ESOPHAGUS 

Beginning  with  the  oesophagus,  we  encounter  an  arrangement 
of  layers  of  muscle  and  fibrous  tissue,  constituting  the  walls  of  a 
tube,  lined  with  mucous  membrane,  which  continues  throughout 
the  rest  of  the  alimentary  canal.  The  part  of  the  tube  below  the 
oesophagus  possesses  in  addition  a  serous  covering,  derived  from 
the  peritoneum,  on  the  outside. 

The  walls  of  the  oesophagus  are  made  of  the  following  layers 
from  within  out :  Mucous,  muscularis  mucosae,  submucous,  mus- 
cular, and  fibrous. 

The  mucous  membrane  is  covered  with  stratified  squamous  epi- 
thelium, resting  on  a  layer  of  connective  tissue,  which  presents 
minute  papillae. 

The  muscularis  mucosce  consists  of  a  small  amount  of  unstri- 
ated  muscle,  lying  below  the  mucous  membrane.  The  fibers  run 
longitudinally. 

The  submucous  layer  is  composed  of  loose  connective  tissue, 
which  accommodates  itself  to  the  contractions  of  the  muscular 
portion,  and  permits  the  mucous  membrane  to  be  thrown  into 
folds.  The  blood-vessels,  lymphatics,  and  nerves  are  distributed 
through  the  submucous  layer  to  the  other  structures.  Mucous 
glands  are  found  in  the  submucous  tissue.  Their  contents  reach 
the  surface  by  means  of  ducts. 

The  muscular  coat  consists  of  an  inner  layer,  fibers  of  which  run 
in  a  circular  direction  about  the  oesophagus,  and  of  an  outer  longi- 
tudinal layer.  In  the  upper  third  of  the  oesophagus  the  muscle  is 
striated,  in  the  lower  third  it  is  unstriated,  and  in  the  middle 
third  the  two  kinds  are  found  mixed. 

PRACTICAL    DEMONSTRATIONS 

Tke  tongue,  taste-buds,  tonsils,  and  oesophagus  should  be  studied  in  this 
connection.  The  taste-buds  may  easily  be  obtained  in  sections  of  the  papilla? 
foliatse  of  the  rabbit's  tongue.  The  tongue  itself  should  be  secured  from  one 
of  the  lower  animals,  and  sections  that  pass  through  the  papilla  should  be 
sketched.  The  papillae  make  beautiful  objects  in  stained  sections.  The  ton- 
sils of  a  human  subject  should  be  used.  The  sections  of  the  tonsil  must  be 
very  thin.  The  oesophagus  may  be  taken  from  one  of  the  lower  animals. 
These  tissues  may  be  hardened  in  alcohol,  or,  better,  in  Orth's  mixture  of 
Miiller's  fluid  and  formaldehyde.  They  may  be  cut,  stained  with  hsematoxylin 
and  eosin,  and  mounted  in  the  usual  manner. 


THE    STOMACH   AND    INTESTINES  151 


THE   STOMACH   AND   INTESTINES 

The  stomach  and  intestines  are  lined  with  mucous  membrane^ 
i.e.,  a  membrane  containing  epithelial  cells,  usually  of  the  columnar 
variety,  which  secrete  mucus. 

The  gastric  and  intestinal  walls  are  constructed  as  follows: 

1.  The  epithelial  lining. 

2.  The  mucosa. 

3.  The  muscularis  mucosce. 

4.  The  submucosa. 

5.  The  muscular  walls  proper. 

6.  The  fibrous  or  peritoneal  investment. 

In  descriptive  anatomy,  the  first  three  of  the  above  are  included 
in  the  mucous  coat. 

The  epithelium  of  the  inner  surface  of  that  portion  of  the 
alimentary  tract  under  consideration  is  of  the  columnar  variety. 
Variations  occur  in  the  deeper  layers,  which  will  be  referred  to 
later  on. 

The  mucosa,  with  its  epithelial  covering,  is  thrown  into  coarse 
folds,  rugce  or  valve -like  reduplications,  which  greatly  increase  the 
extent  of  surface.  It  contains  the  principal  glands  and  capillary 
blood-vessels.  The  epithelial  lining  is  usually  considered  as  a  part 
of  the  mucosa. 

The  muscularis  mucosas  is  a  thin  layer  of  involuntary  muscular 
fiber,  which  separates  the  mucosa  from  the  submucosa.  Some  of 
the  cells  run  in  a  longitudinal  and  others  in  a  circular  direction. 

The  submucosa,  composed  of  loose  areolar  tissue,  serves  to  con- 
nect the  previous  structures  with  the  muscular  coat  proper,  and 
contains  the  larger  trunks  from  which  the  capillaries  of  the  mucosa 
take  their  origin,  or  into  which  they  empty.  An  intricate  plexus 
of  lymphatics  is  also  situated  here. 

The  muscular  coat  consists  of  strong  bands,  running  chiefly  in 
two  directions,  corresponding  to  an  inner  circular  and  an  outer 
longitudinal  layer.  Near  the  cardiac  end  there  is  an  imperfectly 
developed  oblique  layer.  The  muscle -plates  are  sustained  by  con- 
nective tissue. 

A  peritoneal  investment  covers  the  organs,  except  at  such  points 
as  are  occupied  by  the  entrance  and  exit  of  blood-vessels  and  lym- 
phatics through  the  mesenteries,  with  a  few  exceptions. 


152 


STUDENTS   HISTOLOGY 


THE    STOMACH 

The  mucosa  everywhere  contains  microscopical  depressions,  the 
gastric  tubules  or  glands.  These  are  concerned  in  the  production 
of  the  gastric  juice. 

The  several  layers  of  the  stomach  may  be  better  understood  by 
reference  to  the  diagram  (Fig.  100). 

The  gastric  tubular  glands  are  of  two  principal  varieties;  viz., 

1,  the  peptic  glands,  found  in  the  cardiac  portion  of  the  stomach; 

2,  the  pyloric  glands,  which  occupy  the  pyloric  extremity  of  the 


FIG.  100.    DIAGRAM  OF  THE  WALL  OF  THE  STOMACH  IN  VERTICAL  SECTION. 

A.  Layer  of  gastric  tubules. 

B.  Vascular  portion  of  mucosa. 

C.  Muscularis  mucosag. 

D.  Submucosa. 

E.  Internal  circular  layer  of  muscular  fiber. 

F.  External  oblique  and  longitudinal  muscular  layers. 

G.  Peritoneum. 

I,  I,  I.  Lumen  of  gastric  tubules. 
J,  J.  Branching  gastric  tubules. 

K,  K.  Blood-vossels  arising  from  lower  portion  of  mucosa 
forming  plexuses  between  the  tubules. 

organ.  The  mucous  membrane,  midway  between  the  cardiac  and 
pyloric  portions,  is  occupied  by  tubules  which  partake  of  the 
character  of  both  peptic  and  pyloric  glands,  so  that  no  sharp 
boundary  line  exists. 


THE    STOMACH 


153 


The  peptic  or  cardiac  gland -tubes  penetrate  to  the  muscularis 
mucosa?.  They  pursue  a  somewhat  wavy  course,  and  at  their  lower 
or  blind  extremity  are  frequently  bifid.  They  are  lined  at  their 
commencement  on  the  surface  with  translucent  columnar  epithe- 
lium, the  cells  being  polygonal  in  transverse  section.  As  the 
fundus  or  bottom  of  the  tube  is  approached,  the  lining  cells  become 
granular,  larger,  and  somewhat  polyhedral.  Next  the  wall  of  the 
tube  large,  granular,  bulging  cells  are  scattered  irregularly.  The 
epithelium  occupies  the  major  portion  of  the  space  in  the  tube,  so 
that  the  lumen  is  very  small. 

A  single  bifid  tube  is  represented  in  Fig.  101.     The  prominent 


EIG.  101.     VERTICAL  SECTION  OF  A  PEPTIC  TUBULAR  GLAND,  PROM  CARDIAC 
MUCOSA  OF  STOMACH.     LARGELY  DIAGRAMMATIC. 

A.  Central  or  chief  cells. 

B.  Border  or  parietal  cells. 


distinguishing  feature  of  the  peptic  or  cardiac  tubules  is  afforded 
by  the  large  border  or  parietal  cells.  The  cells  next  the  lumina  are 
called  central  or  chief  cells. 

The  pyloric  gland -tubes  pursue  a  course  not  greatly  unlike  that 
of  the  tubes  just  mentioned.  They  do  not  branch,  however,  until 
they  have  penetrated  well  down  toward  the  muscularis  mucosae. 
Their  distinguishing  character  is  afforded  by  the  epithelial  lining. 
At  the  surface,  the  cells  are  columnar,  with  polygonal  transection. 


154  STUDENTS   HISTOLOGY 

The  deeper  parts  are  lined  with  translucent  cylinders.  The  lumina 
are  larger  than  those  of  the  peptic  tubes. 

The  gastric  gland -tubes  are  placed  thickly  side  by  side,  their 
bases  reaching  the  muscularis  mucosa?.  Between  and  beneath  the 
tubes  is  a  dense  network  of  blood -capillaries. 

The  remainder  of  the  stomach  has  little  special  interest  for  the 
histologist.  The  muscular  portion  of  its  walls  consists  of  a  thin 


FIG.  102.     VERTICAL  SECTION  OP  TORTUOUS  AND  BRANCHING  TUBULAR  GLAND, 
PROM  PYLOUIC  MUCOSA  OP  STOMACH.     DIAGRAMMATIC. 

A.  Lumen.    This  is  often  much  widened. 

B.  Duct  portion  of  tubule. 

C.  Bi-anching  glandular  portion,  or  fundus. 

D.  Transverse  section  of  the  fundus. 

E.  Lower  limit  of  mucosa. 

internal  circular  layer,  with  oblique  bundles  interspersed,  and  a 
thin  external  longitudinal  layer,  both  being  of  the  involuntary 
variety.  Between  the  two  layers  is  found  a  plexus  of  non-medul- 
lated  nerves,  corresponding  to  the  plexus  of  Auerbach,  and  another 
in  the  submucosa,  corresponding  to  the  plexus  of  Meissner  of  the 
intestines,  but  they  are  not  usually  demonstrable  by  ordinary 
methods  or  sections. 

The  blood -supply  is  received  at  the  curvatures.  Branches 
penetrate  the  muscular  layers  along  the  lines  of  omental  attach- 
ment, as  blood-vessels  never  penetrate  the  peritoneum. 

The  peritoneum  is  constructed  mainly  of  fibrous  tissue,  with  an 
external  investment  of  endothelium. 


THE   STOMACH 


155 


PRACTICAL    DEMONSTRATION 

Inasmuch  as  the  human  stomach  cannot  often  be  obtained  until  decompo- 
sition has  destroyed  it  for  our  work,  we  must  secure  the  organ  from  some  one 
of  the  lower  animals.  The  stomach  of  the  dog  presents  all  the  histologTcaT 
features  of  that  of  man,  and  can  be  obtained  in  good  condition  from  an  animal 
recently  killed. 

Harden  small  pieces  in  strong  alcohol,  and  cut  sections  at  a  right  angle  to 
the  surface  and  from  different  regions.  Stain  with  hsematoxylin  and  eosin,  and 
mount  in  balsam. 


VERTICAL    SECTION    OF    WALL    OF    CENTRAL     PORTION 


OF   DOG'S   STOMACH 


103) 


OBSERVE: 
(L.) 

1.  The  division  into:     (a)   Surface  epithelium   (free  ends  of 
gland-tubes).    (&)  Mucosa.    (c)  Muscularis  mucosae.    (cO  Sub- 


FIG.  103.    VERTICAL  SECTION  OP  WALL  OF  CENTRAL  PORTION  OF  DOG'S  STOMACH. 

A.  Internal  surface,  showing  open  mouths  of  the  gastric  tubules,  lined  with  clear  colum- 
nar cells. 

B.  Deepest  portion  of  mucosa.  (\   Muscularis  mucosse. 
D.   Submucosa.  E.  Adipose  tissue  in  last. 
F.   Bundles  of  muscular  tissue  (internal  circular)    (X  60). 


156  STUDENTS   HISTOLOGY 

mucosa.     (e)   Muscular  layers.     (Only  a  portion  of    the    inner 
circular  layer  is  shown.     It  has  been  divided  transversely.) 

(H.) 

2.  The  epithelium  of  gland-tubes.     (The  upper  portion  of  the 
tubes  will  be  cut  obliquely  in  many  places,   as  they  have  been 
inclined,   and  the  epithelium  will  show  as  a  beautiful  mosaic  of 
polygonal  areas.)      (a)    The  differentiation  between  border  and 
central  cells.     (&)  Tubes  cut  transversely,  showing  the.lumina. 
(c)  Indications  of  the  capillary  plexuses  between  the  tubes. 

3.  The    mucosa.      («)  Arterioles    and    venules    beneath    the 
tubules.     (6)  Scattered  lymphoid  cells  (round  cells  with  one,  two, 
or  three  nuclei). 

4.  Lenticular  glands,  masses  of  adenoid  or  lymphoid  tissue  at 
the  bottom  of  the  mucous  membrane,  chiefly  near  the  pylorus. 

5.  The  muscularis  mucosae.      (Note  the  elongated  nuclei  of 
the  smooth  muscle-cells.) 

6.  The  submucosa.     (a)  Arteries,  veins,  etc.,  cut  in  various 
directions.     (6)  The  adipose  tissue.     (Fat-crystals  are  frequently 
seen  in  the  cells  when  freshly  mounted.) 

7.  The  muscular  bundles  of  the  circular  layer  with  the  septa 
of  connective  tissue.     (Note  particularly  the  various  appearances 
presented  by  bundles  of  involuntary  muscular  fiber  when  cut  in 
different  planes.) 

8.  Groups  of  ganglion  cells  belonging  to  the  plexuses  of  Auer- 
bach    or    Meissner   will    occasionally    be    seen    on    very    careful 
examination. 

SMALL   INTESTINE 

The  histology  of  the  intestines,  both  large  and  small,  is  formed 
upon  the  general  plan  of  that  of  the  stomach.  The  same  layers 
are  presented:  the  mucosa,  with  its  epithelial  covering;  the  muscu- 
laris mucosce;  the  submucosa;  the  muscular  and  peritoneal  coats. 

The  mucosa  of  the  small  intestine  is  everywhere  pierced  by 
blind  depressions;  and  the  surface  is  studded  with  minute  eleva- 
tions or  papillae,  between  which  are  the  depressions  which  corre- 
spond to  the  tubules  of  the  stomach.  The  elevations  are  called  villi, 
the  depressions  between  the  villi,  the  crypts  of  Lieberkiilm. 

The  small  intestine  serves  two  important  functions:  1.  The 
secretion  of  a  fluid,  one  of  the  digestive  juices — the  succus  enteri- 
cus.  2.  The  absorption  of  food,  especially  the  fats  or  hydrocarbons. 


SMALL    INTESTINE  157 

We  shall  view  the  histology  of  this  organ  from  a  physiological 
standpoint,  considering:  (1)  Those  structures  concerned  in  the 
wretion  of  the  succus  entericus;  (2)  Those  portions  concerned  in 
absorption  of  food. 


JIISTOLOGY    OF    THOSE     PARTS    OF    THE    SMALL    INTESTINE    PARTICU- 
LARLY  CONCERNED   IN   THE    PRODUCTION   OF   THE 
SUCCUS   ENTERICUS. 

The  diagram  (Fig.  104)  is  intended  to  represent  at  A  the  thick- 
ness of  the  mucosa  with  its  papillary  elevations — the  villi.  The 
miiscularis  mucosas  B,  from  which  the  villi  arise,  separates  the 
mucosa  from  the  snbmucosa  C.  The  horizontal  line  at  the  bottom 
of  the  diagram  indicates  the  outer  limit  of  C  and  the  beginning  of 
the  circular  muscular  coat  of  the  intestine.  The  villi,  everywhere 
covered  with  columnar  epithelium,  often  containing  goblet -cells, 
are  represented  in  the  drawing  as  widely  separated.  The  crypts  of 
Lieberkiihn,  which  are  lined  by  columnar  epithelium,  open  between 
the  prominences.  In  the  interior  of  each  villus  is  a  fine  network 
of  Hood -capillaries  (G,  G).  (In  the  specimen  from  which  the 
sketch  was  made  the  blood-vessels  had  been  injected  with  colored 
gelatin  to  make  them  prominent.)  The  cells  on  the  borders  of 
the  crypts  secrete  certain  fluid  material  from  the  blood  circulat- 
ing in  the  capillary  plexuses,  and  pour  it  out  into  the  crypts  ; 
the  crypts  becoming  filled  with  the  fluid,  the  latter  overflows  and 
passes  into  the  lumen  of  the  gut,  to  act  in  promoting  digestion. 
This  is  one  source  of  the  succus  entericus,  and  there  is  yet  another. 

Between  the  bases  of  some  of  the  villi,  tubes  or  ducts  will  be 
found  which,  piercing  the  muscularis  mucosae,  reach  the  sub- 
mucosa,  where  they  branch,  become  convoluted,  are  lined  with 
secreting  cells,  and  are  known  as  the  glands  of  Brunner.  They 
occur  in  the  duodenum  and  are  continuations  of  the  pyloric  glands 
of  the  stomach.  These  glands  are  surrounded  by  blood -capillaries, 
and  the  gland -cells  secrete  a  fluid  which  is  poured  into  the  gut 
between  the  villi,  when  it  becomes  mingled  with  the  secretion 
previously  mentioned,  and  constitutes  a  part  of  the  succus 
entericus. 

We  have, 'then,  seen  that  the  succus  entericus  is  secreted  partly 
from  the  epithelial  cells  lining  the  crypts  of  Lieberkuhn,  and  partly 
from  the  cells  of  Brunner  Js  glands. 


158 


STUDENTS   HISTOLOGY 


FIG.   104.     DIAGRAM   SHOWING  PORTIONS  OP  INTESTINAL  Mucous  MEMBRANE    CON- 
CERNED IN  THE  SECRETION  OP  THE  Succus  ENTERICUS. 

A.  The  mucosa. 

B.  Muscularis  mucosaa. 

C.  Submucosa. 

D.  D,  D.    Villi. 

E.  Crypts  of  Lieberkiihn. 
G.    Blood-plexuses  of  villi. 

H,  H.    Large  vessels  of  submucosa,  supplying  the  epithelium  covering  the  villi. 

I.    Neck  of  a  gland  of  Brunner. 

J.    Gland  of  Brunner  in  the  submucosa. 


THE   REMAINING   STRUCTURES   OF   THE   INTESTINE   CONCERNED 
MAINLY   IN  FOOD   ABSORPTION 

The  diagram  (Fig.  105)  is  intended  to  show  the  same  layers  as 
were  indicated  in  the  previous  figure  (Brunner 's  glands  and  the 
blood-vessels  have  been  omitted  in  order  to  avoid  confusion).  The 
villi  are  represented  much  shortened. 


SMALL   INTESTINE 


159 


In  the  center  of  each  villus  is  the  blind  tube  G,  G,  a  part  of  the 
lymphatic  system,  and  here  called  a  lacteal.  When,  during  diges- 
tion, the  minute  globules  of  fatty  food  reach  the  small  intestine, 
they  are  grasped  by  the  epithelial  cells  covering  the  villi,  and  ar* 
carried  eventually  within  the  body  of  the  villus  to  this  lacteal. 

The  lacteals  pierce  the  muscularis  mucosae,  and  in  the  submu- 
cosa  are  in  connection  with  a  plexus  of  lymphatic  tubes  and  spaces. 
They  eventually  unite  with  efferent  lympli- tubes,  J,  which  open 
into  the  lymphatics  of  the  mesentery. 

Connected  with  the  plexus  of  lymphatics  in  the  submucosa  are 
minute  nodules  of  lymphoid  or  adenoid  tissue,  which  have  unfortu- 
nately been  called  lymphatic  glands.  They  are  in  no  sense  glands. 


D- 


FIG.    105.     DIAGRAM   SHOWING   PORTIONS   OP    INTESTINAL   Mucous   MEMBRANE  CON- 
CERNED IN  ABSORPTION. 

A.  Mucosa. 

B.  Muscularis  mucosae. 

C.  Submucosa. 

D.  D.    Villi. 

F,  F.    Crypts  of  Lieberkiihn. 

G,  G.    Lacteals. 

H,  H.    Chinks  arid  intercommunicating  channels  of  the  lymph-plexus  of  the  submucosa. 
I.    Bottom  of  a  mass  of  adenoid  or  lymphoid  tissue  —  a  so-called  solitary  gland.    Peyer's 
patches  are  formed  of  aggregations  of  these  nodules. 
J.    Efferent  lacteal  or  lymph  duct. 

Slit  up  a  portion  of  intestine  along  the  attached  border,  and 
carefully  examine  the  inner  surface :  it  will  present  a  velvety 
appearance,  due  to  the  minute  villi.  You  will  also  find  little 
nodules,  perhaps  one  or  two  millimeters  in  diameter,  scattered  here 


160  STUDENTS   HISTOLOGY 

and  there  in  the  mucous  coat.  These  are  the  lymphatic  nodules 
alluded  to  above — the  so-called  solitary  glands.  One  of  the  nodules 
is  indicated  in  the  diagram  at  I,  with  its  point  projecting  between 
the  villi  at  F. 

Continuing  your  examination  of  the  gut,  you  will  discover, 
especially  in  the  ileum,  roughened  patches  perhaps  five  to  ten 
centimeters  long  by  one  to  two  centimeters  broad.  These  are 
collections  of  the  lymphatic  nodules  described  in  the  last  para- 
graph, -and  are  termed  agminate  glands,  or  patches  of  Peyer.  They 
have  no  secretive  power,  being  simplj'  in  connection  with,  and  a 
part  of,  the  chain  of  lymphatics  in  the  walls  of  the  intestine.  They 
consist  of  lymphoid  or  adenoid  tissue,  which  will  be  described 
with  the  lymphatics. 

To  recapitulate,  the  small  intestine  presents  the  following: 

1.  The  mill ,  each  containing  a  plexus  of  blood -capillaries  and 
the  lymphatic  or  absorbent  vessel. 

2.  Crypts  or  follicles  of  LieberkUhn. 

3.  Brunner's  glands. 

4.  Solitary  lymphatic  nodules,  the  so-called  solitary  glands. 

5.  Agminate   lymphatic  nodes,   agminate    glands  or  patches  of 
Peyer,  consisting  of  aggregations  of  lymphatic  nodules  similar  to 
the  solitary  lymph -follicles. 

The  muscular  part  of  the  intestine  is  arranged  not  unlike  that 
portion  of  the  stomach:  i.  e.,  with  an  inner  circular  and  an  outer 
longitudinal  layer.  Between  the  two  is  located  Auerbach' s  plexus 
of  non-medullated  nerves.  A  similar  plexus,  Meissner's,  is  found 
in  the  submucosa.  The  ganglia  may  rarely  be  seen  in  ordinary 
sections. 

A  small  quantity  of  areolar  tissue  connects  the  external  longi- 
tudinal muscular  layer  with  the  peritoneal  investment. 

PRACTICAL     DEMONSTRATION 

The  intestines  of  the  dog  or  rabbit  are  more  commonly  used  for  practical 
work,  for  reasons  already  alluded  to.  The  tissue  should  be  cut  into  small 
pieces,  and  hardened  quickly  in  alcohol.  When  human  intestine  can  bo 
obtained  fresh,  a  piece,  say  three  inches  long,  should  be  emptied  of  its  con- 
tents, filled  with  alcohol  by  tying  the  ends,  and  the  whole  hardened  in  strong 
spirit.  Under  no  circumstances  should  the  gut  be  washed,  and  great  care  must 
be  taken  to  avoid  injuring  the  delicate  cells  covering  the  villi.  Vertical  sec- 
tions with  the  microtome  are  the  most  valuable.  Stain  with  hsematoxylin  and 
eosin,  and  mount  permanently  in  balsam. 


SMALL   INTESTINE 


161 


VERTICAL     SECTION     OF     THE     ILEUM,    INCLUDING     PORTION     OF     A 
PATCH    OF    PEYER.      HUMAN      ( Vide  Fig.  106) 

OBSERVE  : 

(L.) 

1.  The  villi.     (a)  That  they  are  of  varying  lengths,  slender, 
wavy  and  delicate.     (&)  The  covering  of  columnar  cells.     (The 


FIG.  106.     INTESTINAL  Mucous  MEMBRANE   THROUGH  A  PEYER'S   PATCH.    VERTICAL 
SECTION.     STAINED  WITH  H^MATOXYLIN  AND  EOSIN  (X250). 

A,  A.  A.    Villi. 

B.  Transverse  sections  of  crypts  of  Lieberkiihn. 

C,  C.    Crypts  in  vertical  section. 

D,  D,  D.    Nodules  of  lymphoid  tissue— constituting  a  patch  of  Peyer. 

E.  Muscularis  mucosae. 

F.  Submucosa. 

free  extremities  of  many  of  the  villi  in  the  drawing  are  seen 
broken,  and  the  epithelium  is  wanting  in  places.  It  is  almost 
impossible  to  secure  perfect  villi  from  human  intestine,  on  account 
of  the  length  of  time  usually  intervening  between  death  and  the 
removal  of  the  tissue.)  (c)  Oblique  sections. 

2.  The  crypts  of  Lieberkiihn. 

3.  The  lymphatic  nodules  (so-called  solitary  glands),  consti- 
tuting the  elements  of  a  patch  of  Peyer.     (a)  Their  projection 
upon  the  mucous  surface   of   the   gut  between  the  villi.     (&) 
The  covering  with  epithelium  on  their  free  borders.     (They  are 

K 


162  STUDENTS   HISTOLOGY 

located,  properly  speaking,  in  the  submucosa  and  between  the 
villi.  In  the  drawing,  their  bases  do  not  all  appear  in  the  sub- 
mucosa, inasmuch  as  the  nodules  are  cut  in  different  planes.) 

4.  Muscularis  mucosae.    The  elongated  nuclei  of  the  involun- 
tary muscular  elements. 

5.  The    submucosa.      (a)  The    blood-vessels.      (ft)  Lymph- 
spaces.     (Lymphatic  channels  are  very  irregular  in  form  and  size, 
and  are  often  mistaken,  in  sections,  for  ruptures  in  the  connective 
tissue.     The  stained  nuclei  of  the  endothelial  cells,  with  which  all 
lymph -channels  are  lined,  will  enable  one  to  differentiate.) 

(HO 

6.  The  villi.     (a)  The  covering  columnar  cells.     (&)  Goblet 
cells  scattered  between  the  last.     (These  goblet  or  mucous  cells 
are  well  shown  in  the  intestine  of  the  dog  or  rabbit.)     (c)  The 
lacteals.     (These   are  not    plainly   demonstrable,   under  ordinary 
circumstances,  in  human  tissue.     Sections  from  the  gut  of  a  dog, 
killed  during  the  active  digestion  of  materials  rich  in  hydrocarbons, 
will  show  them  filled  with  minute  fat -globules.)     GO  The  basis 
tissue,  a  fibrous  reticulum  containing  many  lymphoid  cells,     (e) 
Portions  of  the  capillary  plexuses. 

7.  Blood-vessels  of  the  mucosa  below  the  villi. 

8.  The  lymphoid  or  adenoid  tissue  of  the  lymph -nodules. 

Mount  also  sections  of  (1)  DUODENUM,  to  show  Brunner's  glands,  which 
occur  there  only.  (2)  LARGE  INTESTINE  (human), -which  has  no  villi  nor  val- 
vulse  conniventes.  The  crypts  of  Lieberkiihn  and  solitary  follicles  are  abun- 
dant. (3)  VERMIFORM  APPENDIX  (human),  observe  the  abundant  lymphoid 
tissue . 


THE   LIVER  163 


THE   LIVER 

This  great  gland  is  covered  with  a  fibrous  membrane — the  cap- 
sule of  Qlisson.  The  capsule  is  covered  with  a  single  layer  of  ir- 
regularly shaped,  flat  endothelial  cells. 

Prolongations  from  the  fibrous,  visceral  portion  of  Glisson's 
capsule  penetrate  the  organ  from  every  side,  and  divide  the  entire 
structure  into  compartments — the  lobules. 

The  hepatic  lobules  are  irregularly  polygonal  in  transverse  sec- 
tion, and  somewhat  ovoid  vertically.  They  are  about  two  milli- 
meters in  diameter. 

Let  us  first  examine  the  general  plan  of  the  vascular  arrange- 
ment, and  later,  the  minute  structure  of  the  lobular  parenchyma. 

The  hepatic  blood -supply  comes  from  two  sources:  1.  The 
venous  drainage  collected  in  the  portal  vein.  2.  The  arterial  sup- 
ply, provided  from  the  aorta  by  the  hepatic  artery.  The  portal 
venous  blood  is  filtered  through  the  liver  instead  of  passing  directly 
to  the  ordinary  destination  of  venous  blood  (the  vena  cava),  in 
order  to  contribute  certain  factors  to  the  processes  of  digestion  and 
metabolism,  while  the  smaller  arterial  supply  is  distinctly  nutritive. 
The  hepatic  duct  is  the  common  excretory  conduit  of  the  bile  after 
its  formation  by  the  parenchyma  of  the  liver. 

The  scheme  of  the  organ  will  be  understood  by  reference  to 
Fig.  107,  which  is  purety  diagrammatic. 

The  portal  vein  enters  the  liver  at  the  transverse  fissure.  It 
divides  and  subdivides;  and,  reaching  every  part  of  the  various 
lobes,  the  terminal  twigs  are  seen  in  the  connective  tissue  of  the 
walls  of  the  lobules. 

Branches  from  these  termini  of  the  portal  or  interlobular  veins 
penetrate  the  lobular  areas,  and  immediately  break  up  into  capil- 
laries, which  form  an  intricate  plexus  throughout  the  lobule.  The 
blood  from  these  capillaries  is  finally  collected  into  a  central  or 
intralobular  vein,  by  means  of  which  it  is  immediately  drained  from 
the  lobule. 

The  central  veins  from  a  varying  number  of  the  lobules  unite 
outside  of  the  latter,  forming  the  beginning  of  the  hepatic  or  so- 
called  sublobular  veins;  and  sublobular  veins  from  various  lobular 
areas  unite,  forming  several  (six  or  seven)  large  hepatic  veins,  which, 
passing  in  the  connective  tissue  framework,  finally  drain  the  blood 


164 


STUDENTS   HISTOLOGY 


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from  the  organ  and  pour  it  into  the  ascending  cava  as  it  lies  pos- 
teriorly in  its  fissure. 

The  hepatic  artery  also  penetrates  the  transverse  fissure.  It 
accompanie^  the  portal  vein  in  its  ramifications,  giving  off  nutrient 
twigs  to  the  connective  tissue  framework  and  to  the  walls  of  the  ves- 
sels. The  terminal  branches,  very  minute,  pour  any  remaining 


THE   LIVER  165 

blood  into  the  venous  plexus  at  the  margin  of  the  lobules,  thus 
providing  arterial  blood  for  the  lobular  parenchyma. 

The  hepatic  duct  is  also  seen  emerging  from  the  transverse  fis- 
sure. (For  the  sake  of  clearness,  we  will  trace  it  from  without  in- 
ward.) It  follows  the  course  of  the  portal  vein  with  the  hepatic 
artery.  Wherever  in  a  section  of  the  organ  the  portal  is  divided, 
the  artery  and  duct  will  also  appear.  Bound  together  with  con- 
nective tissue,  the  trio  reach  the  walls  of  the  lobules.  The  ducts 
now  penetrate  the  lobule  and  break  up  into  an  exceedingly  minute 
plexus — the  bile -capillaries.  This  plexus  properly  begins  in  the 
lobules  and  drains  the  bile  as  formed,  passing  it  into  the  ducts  in  a 
direction  opposite  to  the  portal  blood -current. 

THE    PORTAL    CANALS 

If  it  were  possible  to  grasp  the  vessels  as  they  are  found  emerg- 
ing at  the  transverse  fissure,  the  portal  vein,  hepatic  artery,  and 
hepatic  duct,  and  to  forcibly  tear  them,  with  their  supporting  con- 
nective tissue,  out  of  the  liver,  a  series  of  channels  or  canals  would 
thereby  be  formed.  A  portal  canal,  then,  is  a  space  in  the  liver 
occupied  by  branches  of  the  portal  vein,  the  hepatic  artery,  and  the 
hepatic  duct,  and  the  contiguous  connective  tissue.  Frequently  more 
than  one  specimen  of  each  vessel  is  to  be  seen  in  a  canal.  There 
may  be  two  or  three  veins,  and  as  many  arteries  and  ducts,  asso- 
ciated in  a  single  portal  canal.  Lymphatic  chinks  are  also  abun- 
dant in  this  connective  tissue. 

From  what  has  been  said,  it  will  be  understood  that  a  vessel 
found  by  itself  in  this  organ  must  be  either  an  intralobular  or  a 
hepatic  vein;  and  these  are  easily  distinguished,  as  the  former  are 
within,  while  the  latter  are  without  the  lobules  and  in  the  connec- 
tive tissue  framework.  On  the  other  hand,  a  group  of  vessels  will 
indicate  a  portal  canal,  with  its  large  and  thin -walled  vein,  the 
small  thick-walled  artery,  and,  intermediate  in  size,  the  duct. 

THE   LOBULAR    PARENCHYMA 

The  lobules  consist  of  two  capillary  plexuses,  one  containing 
blood  and  the  other  bile.  In  the  meshes  of  this  network,  the 
hepatic  cells  are  located. 

The  blood -capillaries,  although  extremely  tortuous,  have  a  gen- 
eral direction  of  convergence  toward  the  central  veins.  This  is 


166 


STUDENTS   HISTOLOGY 


best  seen  when  the  lobules  have  been  divided  in  a  vertical  di- 
rection. 

The  bile -capillaries  are  among  the  smallest  canals  found  in  vas- 
cular tissues,  having  a  diameter  of  only  1  to  2  /*.  They  pursue  a 
direction  in  the  human  liver,  as  a  rule,  at  right  angles  to  the  course 
of  the  blood -capillaries,  and  are  not  demonstrable,  except  with 
considerable  amplification,  say  X  400,  and  then  only  in  the 
thinnest  portion  of  the  sections.  They  are,  properly  speaking, 
merely  minute  channels  in  the  parenchyma,  and  have,  it  is 
believed,  no  wall. 

The  hepatic  cells  are  polyhedral,  about  twice  the  size  of  a  white 
blood-corpuscle,  say  from  20  to  25  ^  in  diameter,  usually  with  a 
single  nucleus  and  with  granular  protoplasm,  frequently  contain- 


FIG.  108. 


DIAGRAM  ILLUSTRATING  THE  INTRALOBULAR 
HISTOLOGY  OF  THE  LIVER. 


The  hepatic  cells  are  connected  in  columns  between  the  blood-capillaries.  The  cells  are 
endowed  with  the  power  of  selecting  especially  such  materials  from  the  blood  as  are  necessary 
for  'the  manufacture  of  bile.  Having  accomplished  this,  the  secreted  fluid  is  given  up  to  the 
bile-capillaries,  and  by  them  poured  into  the  ducts,  and  led  out  of  the  liver  for  subsequent  use. 
The  direction  of  the  pressure  is  indicated  by  the  arrows.  This  is  the  histology  of  gland-struc- 
tures generally. 

ing  minute  fat-droplets  and  granules  of  yellow  pigment.  The  ex- 
istence of  a  definite  limiting  membrane  has  been  questioned,  as  far 
as  the  cell  of  the  human  liver  is  concerned,  although  such  a 
structure  can  be  shown  in  many  of  the  lower  animals. 

The  physiological  plan  of  the  intralobular  structure  is  expressed 
in  the  diagram,  Fig.  108.  The  blood  is  brought  into  relation  with 
the  lobular  parenchyma — the  hepatic  cells — by  the  capillary  plexus, 


THE   PARENCHYMA    OF   THE   LIFER  167 

and  the  elements  necessary  to  constitute  the  bile  are  selected  and 
carried  on,  to  be  drained  away  by  the  bile -capillaries  and -ducts. 

PRACTICAL    DEMONSTRATION 

It  is  best  to  begin  with  the  liver  from  a  pig.  The  amount  of  connective 
tissue  in  the  normal  human  liver  is  very  small,  and  is  mainly  confined  to  the 
support  of  the  interlobular  vessels;  the  boundaries  of  the  lobules  are,  there- 
fore, poorly  defined,  and  without  the  previous  observation  of  some  well  outlined 
specimen  the  student  frequently  gets  but  an  imperfect  notion  of  the  plan  of 
the  human  organ. 

Pieces  of  liver,  say  a  centimeter  square  by  half  a  centimeter  thick,  are 
hardened  by  twenty-four  hours'  immersion  in  strong  alcohol.  Larger  pieces 
may  be  prepared  with  Miiller's  fluid.  Sections  should  be  cut  with  a  microtome, 
care  being  taken  to  include  some  of  the  medium-sized  portal  canals.  The 
portal  vein,  with  its  accompanying  vessels,  may  be  easily  distinguished  from 
the  solitary  and  Jess  frequent  branches  of  the  hepatic  veins.  The  elements  of 
these  canals,  and  especially  the  larger  ones,  are  best  kept  intact  by  infiltration 
of  the  tissue  with  celloidin;  but  very  fine  sections  may,  with  care,  be  made 
from  the  alcohol -hardened  tissue.  Even  free-hand  cuts,  after  some  degree  of 
skill  has  been  obtained  by  practice,  will  answer  very  satisfactorily.  Stain  with 
hsematoxylin  and  eosin. 


SECTION    OF    LIVER    OF    PIG.      CUT    VERTICALLY    TO    AND 
INCLUDING    THE    CAPSULE    OF    GLISSON 

OBSERVE:  (Fig.  109) 

(L.) 

1.  The  capsule  of  Glisson,  C.     (Note  the  prolongations  sent 
into  the  organ,  which  divide  the  entire  structure  into  irregularly 
polygonal   areas — if    divided  transversely — and    elongated,   verti- 
cally-sectioned areas — the  hepatic  lobules.) 

2.  The  central  (intralobular)  veins,  C.  V.    (Note  that  the  figure 
formed  by  the  division  of  the  vein  varies  according  to  the  direction 
of  the  cut,  a  circle,  oval,  or  elongated  slit,  as  the  lobules  have 
been  sectioned  transversely,  obliquely,  or  vertically.) 

3.  The  hepatic  veins,  H.  V.    (Those  shown  in  the  section  are 
undoubtedly  sublobular.     It  must  be  remembered  that  sub  applied 
to  these  vessels  is  misleading,  as  the  lobules  are  situated  on  every 
side,  as  well  as  above  the  sublobular  veins.) 

4.  The  portal  canals,  P.  C.     (Even  the  smaller  ones,  I,  I,  are 
reactily  differentiated   from  areas  containing  hepatic  veins,  inas- 
much  as  a  group   of  vessels   can   be  distinguished — the   hepatic 
veins  running  alone.) 


168 


STUDENTS  HISTOLOGY 


5.  The  portal  veins,  V.  (Observe  that  they  usually  are  the 
largest  vessels  in  the  canals.  Note  their  thin  walls.  They  not 
infrequently  contain  blood- clots,  with  deeply  stained,  scattering, 


FIG.  109.    LIVER  OF  THE  PIG  SECTIONED  AT  A  RIGHT  ANGLE  TO  GLISSON' 
CAPSULE.     STAINED  WITH  H^IMATOXYLIN  AND  EOSIN  (X60). 

C.  Capsule  of  Glisson. 

C.  V.  Central  or  intralobular  veins. 
O.  C.  Oblique  section  of  central  veins. 

1. 1, 1.  Interlobular  veins.     (In  small  portal  canals.) 
P.  C.  A  large  portal  canal. 
A.  A.  Hepatic  arteries. 

D.  Hepatic  duct. 
V.  A  portal  vein. 

H.  V.  Hepatic  veins— probably  sublobular. 


white   corpuscles,   appearing  with   this    amplification    as    dots    or 
granules.) 

6.  Hepatic  arteries,  A.     (The  larger  examples  may  be  deter- 
mined by  their  thick  muscular  media  and  the  wavy  pink  line — the 
fenestrated  membrane.     Several  may  be  seen  in  a  single  canal.) 

7.  Hepatic  ducts,  D.     (These  are  lined  with  cylindrical  epithe- 
lial cells,  hexagonal  in  transverse   section,  and   the  bold,  deeply 


THE   PARENCHYMA    OF   THE    LITER  169 

stained  nuclei  give  the  ducts  marked  prominence  even  with  the 
low -power.  Indeed,  the  smaller  portal  canals  are  frequently  dif- 
ferentiated by  this  element  alone — this  being  especially  true  when 
the  structures  have  been  disturbed,  and  perhaps  torn,  in  the.  pro- 
cess of  mounting.) 

8.  The  lobular  parenchyma.  (The  arrangement  of  the  hepatic 
cells,  forming  branching  columns,  is  merely  indicated — with  the 
low -power — by  their  deeply  stained  nuclei  presenting  granular 
areas  within  the  lobular  boundaries.  Still,  by  careful  attention, 
the  elements  will  be  seen  to  radiate  more  or  less  distinctly  from 
focal  points — the  central  or  intralobular  veins. 

(H.) 

9.  The  portal  veins. 

10.  The  lymph-spaces   in  the  connective  tissue   of  the  portal 
canals.     (Note,  in  those  which  are  better  denned,  the  nuclei  of  the 
endothelium.     Do  not  confound  these  lymphatics  with  small  veins, 
as  the  latter  present  a  tolerably  denned  wall,  while  the  lymphatic 
chinks  appear  like  rifts  in  the  connective  tissue;   it  would  be  diffi- 
cult to  make  this  distinction  without  the  endothelial  cells.) 

11.  Hepatic  arteries.      (On  account  of   its  solidity,  the  liver 
will  enable  the  student  to  secure  sections  of  blood-vessels  present- 
ing the  typical  structure  more  nearly  than  the  specimens  obtained 
from  the  organs  heretofore  examined.)     Note  (a)   the  elongated 
nuclei  of  the  muscular  elements  of  the  media;   (&)  the  fusing  of 
the  adventitia  with  the  connective  tissue  surrounding  the  artery ; 
(c)  the  sharply  defined  outer  boundary  of   the   intima — the    fe- 
nestrated  membrane,  which,   from  the   action  of   the   hardening 
agent,    has    contracted   the    elastic    fibers    and   detached    (d)    the 
endothelial  cells.     (Inasmuch  as  the  lining  cells  of  small  arteries 
are    very  frequently  partly  detached   in    alcohol -hardened   tissue, 
they  may  simulate   columnar  cells.     A  like  appearance    is    often 
presented  when  an  artery  has    been  sectioned  obliquely,   by  the 
projecting  muscle-cells  of  the  media.) 

12.  Hepatic  ducts.     Note  :    (a)    The   lining   cylindrical  cells. 
(&)  The  nuclei  of  these  cells  (as  a  rule,  perfectly  spherical ;   and, 
in  transections  arranged  in  a  circle,  affording  an  appearance  per- 
fectly characteristic).      (c)    Mucous    glands    in   the  wall  of   the 
larger  ducts,  lined  with  large,  nucleated,  columnar  cells,  preeisely 
like  those  lining  the  duct-lumen  ;    and,  hence,   liable  to  be  mis- 
taken for  small  ducts.     (The  tube  carrying  the  mucus  secreted  in 


170  STUDENTS   HISTOLOGY 

i 

these  pocket -like  glands  does  not  pass  directly  into  the  lumen  of 
the  duct,  but  runs  along  obliquely,  much  like  glands  in  the 
bronchi.  Not  infrequently  the  glands  possess  no  proper  efferent 
tube,  but  are  mere  depressions  or  diverticula  in  the  thick  wall  of 
the  bile-duct.) 

13.  The  lobular  parenchyma.  (Single  cells,  partly  detached, 
may  be  found  about  the  edges  of  the  section.)  Note:  (a)  The 
somewhat  polygonal  figure;  (&)  the  nucleus;  (c)  nucleoli ; 
(d)  fibrillated,  mesh-like  cell-body;  and  (e)  an  apparent  cell-wall. 
(The  arrangement  of  the  lobular  parenchyma  will  be  noted  in  con- 
nection with  the  human  liver.) 


HUMAN  LIVER 
PRACTICAL     DEMONSTRATION 

The  sections  from  which  the  illustrations  have  been  drawn  were  made  from 
material  hardened  in  Miiller's  fluid.  The  tissue  was  then  cut,  the  sections 
washed  by  six  hours'  maceration  in  water,  after  which  they  were  treated  suc- 
cessively with  weak  and  stronger  alcohol,  stained  with  hsematoxylin  and  eosin, 
and  mounted  in  balsam.  This  treatment  aids  greatly  in  the  demonstration  of 
the  blood-capillaries,  as  the  contained  blood-corpuscles,  in  consequence  of 
some  change  affected  by  the  chromium  salt,  take  the  eosin  deeply.  The 
nuclei  of  cells  are  also  rendered  markedly  prominent. 

Pieces  of  tissue,  one  centimeter  square  by  half  a  centimeter  thick,  may  be 
hardened  in  alcohol.  This  method  will  give  very  excellent  results,  providing 
the  sections  be  cut  as  soon  as  the  hardening  process  has  become  complete. 
Stain  as  above. 

For  the  demonstration  of  the  isolated  hepatic  cells,  scrape  the  cut  surface 
of  a  piece  of  hardened  liver  with  a  scalpel,  and  throw  the  scrapings  into  a 
watch-glass  of  hasmatoxylin.  After  a  few  moments  drain  off  the  stain,  and 
brush  the  stained  tissue  elements  into  a  test-tube  nearly  filled  with  water. 
Change  the  water  two  or  three  times ;  and  when  clear,  add  a  few  drops  of  eosin 
solution.  Allow  the  eosin  to  stain  for  a  moment  only;  decant,  drain,  and  fill 
the  tube  with  alcohol.  After  ten  minutes  the  spirit  may  be  drained  off  and 
the  tube  partly  filled  with  oil  of  cloves.  A  drop  of  the  sediment  may  then 
be  placed  upon  the  slide,  the  bulk  of  the  oil  removed  with  paper,  and  the 
mounting  completed  by  adding  a  drop  of  balsam  and  the  cover-glass.  This 
tissue  may  be  kept  in  the  oil  from  year  to  year  for  class-room  purposes.  If 
the  oil  be  pure  and  the  washing  thorough,  the  staining  will  remain  unaffected 
for  two  or  three  years. 


HUMAN  LIVER 


171 


SECTION    OF    HUMAN    LIVER,  CUT    AT  A    RIGHT  ANGLE    TO    THE    SUR- 
FACE,   AND     STAINED    WITH     H^MATOXYLIN    AND     EOSIN 

(Fig.  110) 

OBSERVE  : 
(L.) 

1.  The   imperfectly  outlined  lobules   (in   consequence  of  the 
absence  of  interlobular  connective  tissue.) 

2.  The  fusing  of   the   lobules.     (At  points  like   B,   B,   it    is 
impossible  to  say  just  where  one  lobule  ceases  and  the  contiguous 
one  begins.) 


FIG.  110.     SECTION   OP   HUMAN   LIVER.     STAINED  WITH   H^EMATOXYLIN  AND 

EOSIN  (X60). 

A.  A,  A.  Central  veins  sectioned  generally  at  a  right  angle  to  the  lobule. 

B.  B.  Points  where  adjoining  lobules  coalesce.     Illustrating  the  difficulty  of  outlining  the 
lobules  in  normal  human  liver. 

C.  Connective  tissue  of  a  portal  canal. 

D.  Large  interlobular  vein. 

E.  Hepatic  duct  belonging  to  C. 

F.  Hepatic  artery  of  C. 

<J,  <i.  Smaller  portal  canals. 

H.  Small  hepatic  ducts — always  recognizable  by  the  deeply  hseuiatoxyHu-stained   nuclei  of 
thoir  lining  cells. 

I,  I.  Hepatic — sublobular — veins. 


172  STUDENTS   HISTOLOGY 

3.  The    central    (or   intralobular)    veins,    A,    A     (frequently 
appearing  as  mere  slits  on  account  of   the  direction  of  the  cut). 

The  portal  canals,  G,  G.    (These  are  readily  detected  on  account 
of  the  deeply  stained  nuclei  of  the  cells  lining  the  hepatic  ducts.) 
(H.) 

5.  Portal  canals   (too  small  for  demonstration  of  the  several 
elements,  but  always    distinguishable  by   the  columnar   epithelial 
cells.) 

6.  The  larger  portal  canals,  C.     Note:    (a}  The  large  thin- 
walled  vein,  D;    (6)  The  duct,  E;    (c)  The  artery,  F. 

7.  The  tortuous  course  of  the  hepatic  cell-columns  as  com- 
pared with  the  same  in  the  section  previously  studied. 

8.  The  hepatic  veins.     (Observe  their  infrequency  compared 
with  the  sections  of  the  portal  veins.     Note  the  small  amount  of 
connective  tissue  around  them— greater,  however,  than  that  about 
the  central  veins.) 

ELEMENTS     OF    A    PORTAL     CANAL— FROM  PREVIOUS     SECTION 

OBSERVE:  (Fig-  Hi) 

(H.) 

1.  The  portal  vein,  V.     (Note  the  nuclei  of  the  few  endothe- 
lial  cells  remaining,  and  the  corpuscular  elements  of  the  blood 
in  the  lumen  of  the  vein.     Observe  that  the  white  corpuscles  are 
scanty,  and  deeply  stained;  also  that  many  of  the  colored  corpuscles 
are  granular,  and  show  loss  of  pigment  from  action  of  the  alcohol.) 

2.  The  hepatic  artery,  A.     (In  the  human  liver,   the  portal 
canals  frequently  carry  a  number  of  arteries  and  ducts,  instead  of 
one  of  each,  as  shown  in  the  one  selected  for  the  illustration.     The 
arteries  can  nearly  always  be  differentiated  by  the  clear,  wavy  line 
of  the  fenestrated  membrane.     Should  the  section  have  been  in  a 
longitudinal  direction  with  reference  to  the  vessel,   look  for  the 
elongated  nuclei  of -the  unstriated  muscle-cells  of  the  media,  some 
running  with   the   artery — the   longitudinal — and   others  at  right 
angles  to  its  course — the  circular  fibers.) 

3.  The  hepatic  duct,  D.     (Observe  the  thickness  of  the  wall, 
depending,  of  course,  upon  the  diameter  of  the  duct  itself,  and  the 
presence  of   connective  tissue    supporting   scattering  unstriated 
muscle-cells.      Note    the    beautiful,  clear,   columnar    cell-lining. 
That  these  epithelial  cells  are  polygonal  in  transverse  section  is 
demonstrable  at  D,  L,  where  the  duct  has  been  cut  in  a  longitudinal 
way,  and  the  cells  are  seen  from  above. 


HUMAN  LIFER 


173 


FIG.  111.     SECTION  OF  HUMAN  LIVER  SHOWING  THE  ELEMENTS  OF  A  PORTAL  CANAL,. 
STAINED  WITH  ELEMATOXYLIN  AND  EOSIN  (X400). 

A.  Hepatic  artery. 
V.  Portal  vein — interlobular. 
D.  Hepatic  duct  in  T.  S. 
D,  L.  Hepatic  duct  in  L.  S. 
L.  Lymph-space. 
The  lobular  parenchyma  of  contiguous  lobules  will  be  seen  on  the  right,  and  above  the  canal. 

4.  The  connective  tissue  elements  of  the  canal,  reaching  out 
in  various  directions  between  the  adjacent  lobules. 

5.  Lymph-spaces  or  -chinks,  L.     (Note  the  stained  nuclei  of 
the  endothelial  cells.) 

6.  Nerve-trunks.     (In  the  larger  canals  bundles  of  non-medul- 
lated  or  more  rarely  medullated   nerve -fibers  may  be  frequently 
seen.     They  are  not  shown  in  the  accompanying  illustration.) 


PARENCHYMA— STAINED     CELLS    FROM 
PIG'S    LIVER    (Fig.  112) 


HUMAN  AND 


THE  LOBULAR 

OBSERVE  : 
(H.) 

1.  Isolated  hepatic  cells  A,  A.  Note  the  large,  variably- 
sized  nuclei,  their  nucleoli,  and  the  granular  protoplasm  of 
the  cell -body. 


174 


STUDENTS   HISTOLOGY 


2.  Groups    of    cells   forming    portions    of    the    hepatic    cell- 
columns,  as  at  C. 

3.  Cells  containing  fat-globules,  D. 

4.  Glycogen  can  be  demonstrated  in  the  hepatic  cells  of  the 
rabbit  some  hours  after  a  meal  of  carrots.     Harden  in  alcohol; 
cut  without  imbedding;,  stain  with  iodine  solution  '(see  page  29), 
which  colors  glycogen  reddish  brown. 


FIG.   112.     ISOLATED  HEPATIC  CELLS.     STAINED  WITH  H^EMATOXYLIN 
AND  EOSIN  (X  400). 

A.  A.  Cells  from  human  liver. 

B.  Cells  from  same,  showing  below  a  blood-capillary  in  T.  S. 

C.  A  blood-capillary  with  part  of  a  column  of  cells. 

D.  Human  liver  cells  in  a  condition  of  fatty  infiltration. 

E    Isolated  cells  from  liver  of  pig,  showing  intracellular  network. 


THE    LOBULAR    PARENCHYMA,    CONTINUED — SECTION    OF 
HUMAN    LIVER     (Fig.    113) 

Having  found  with  L  a  typical  lobule  in  transverse  section : 

OBSERVE  : 
(H.) 

1.  The    central   vein,    C.  V.     (Note   the   exceedingly   delicate 
wall,  and  search  for  a  trunk  of  the  intralobular  plexus  in  its  con- 
nection with  this  vein.) 

2.  The  blood-capillaries  in  longitudinal  section,  B.C.      (Ob- 
serve their  tortuousness,   bifurcations,   and  anastomoses.) 

3.  Blood  -  capillaries    in    transection,    T.    S.       (Should    the 


HUMAN  LIVER 


175 


capillaries    be    filled    with     blood,    this    demonstration    will     be 
greatly  aided.) 

4.  Hepatic    cell    columns,   H.  C.       (Note   the   difficulty   with 
which  these  can  be-  traced  for  any  great  distance,  on  account,  e£ 
their  irregular  and  twisted  course   throughout  the  lobule.     Ob- 
serve that   the   lobules  are  composed   largely  of   tortuous  blood- 
capillaries,   between  which   the   hepatic  cell -columns  are  placed. 
Note  the  manner  in  which   the  cells  are   disposed  around   the 
blood  capillaries,  as  at  T.  S.) 

5.  Bile-capillaries,  D.     (These  are  rather  difficult  of  demon- 
stration in  the  human  liver.     The    section    should   be   extremely 


FIG.  113.    A  SINGLE  LOBULE  FROM  HUMAN  LIVER.     TRANSVERSE  SECTION. 
STAINED  WITH  H.-EMATOXYLIN  AND  EOSIN  (X  400). 

C.  V.  Central  vein  of  the  lobule. 
B.  C.  Blood-capillaries  in  L.  S. 

T.  S.  The  same  in  transverse  section. 
H.  C.  Columns  of  hepatic  cells. 

D.  Bile-capillaries. 

thin,  and,  in  order  to  get  the  best  results,  a  higher  power 
instrument  than  we  ordinarily  use  will  be  required.  The 
best  point  at  which  to  see  them  is  at  the  junction  of  three 
or  four  cells,  where  the  bile -capillary  has  been  divided  trans- 
versely. 


176 


STUDENTS   HISTOLOGY 


THE  LOBULAR  PARENCHYMA,  CONCLUDED — ORIGIN  OF  THE  BILE- 
DUCTS — SAME  SECTION  AS  BEFORE     (Fig.  114) 
OBSERVE  : 
(H.) 

1.  The  connection  between  the  intralobular  bile-capillaries 
and  the  marginal  or  intralobular  bile-ducts.  (The  manner  of 
connection  between  the  above  is  as  follows  :  The  bile -capillaries 


FIG.   114.    PORTION   OF    THE    PERIPHERY    OF    A    HEPATIC    LOBULE    SHOWING    THE 
ORIGIN  OF  A  BILE-DUCT.     STAINED  WITH  H^MATOXYLIN  AND  EOSIN  (X400). 

A.  Bile-capillaries  in  longitudinal  section. 

B.  Bile-duct.    The  bile-capillaries  are  simply  chinks  between  the  hepatic  cells.     In  the  for- 
mation of  a  duct,  the  hepatic  cells  become  altered  in  shape,  elongated,  and  eventually  become  the 
lining  cells  of  the  duct.    A  little  connective  tissue,  thrown  around  the  outside,  completes  the 
structure  as  seen  at  B. 

C.  Bile-capillary  in  transverse  section.    The  larger  clear  spaces  are  blood-capillaries. 


are  merely  channels  between  the  hepatic  cells,  and  run,  as  a  rule, 
at  a  right  angle  to  the  blood -capillaries.  They  are  probably 
destitute  of  a  wall  in  the  human  liver.  As  these  channels  ap- 
proach the  marginal  part  of  the  lobule,  the  hepatic  cells  surround- 
ing the  capillary  are  seen  to  change  their  form.  They  elongate, 
becoming  thinner,  gradually  losing  their  form  as  hepatic  cells,  and 
assume  a  columnar  type.  At  the  same  time,  a  few  fibers  of  con- 


HUMAN    LIVER 


177 


nective  tissue  are  thrown  outside  the  modified  hepatic  cells,  and  a  bile- 
duct  results.  The  hepatic  cells  become,  insensibly,  the  columnar 
cells  lining  the  duct.  This  is  shown  in  the  illustration  rather 
diagrammatically.  Its  demonstration  requires  much  patient  study 
and  search.  The  duct  is  best  traced  backwards  to  the  point  where 
the  bile -capillaries  enter  it. 

The  study  of  the  blood-  and  bile -capillaries  of  the  liver  is 
much  easier  if  tissues  are  used  in  which  these  vessels  have  been 
injected  with  some  colored  substance.  Injection  of  the  bile -capil- 
laries is  difficult ;  but  injection  of  the  blood -capillaries  is  quite 
readily  accomplished. 

The  structure  of  the  gall-bladder  and  its  duct  is  substantially 
the  same  as  that  of  the  larger  bile -ducts.  The  mucous  membrane 
is  thrown  into  numerous  small  folds,  and  is  covered  by  columnar 
epithelial  cells.  The  mucous  membrane  is  supplemented  by 
unstriated  muscle -fibers,  outside  of  which  is  a  fibrous  layer. 


178  STUDENTS    HISTOLOGY 


THE   KIDNEY 

The  kidney  is  as  singular  in  structure  as  in  function.  Al- 
though as  originally  developed  it  is  divided  into  lobules,  little 
trace  of  this  structure  remains  in  the  adult  organ. 

The  kidney  consists,  essentially,  of  an  intricate  system  of 
blood-vessel  plexuses,  in  intimate  relation  with  a  system  of  urine- 
tubes — the  whole  supported  by  a  small  amount  of  connective 
tissue. 

The  accompanying  drawing  (Fig.  115)  will  serve  to  give  an 
idea  of  the  gross  plan  or  scheme  of  the  structure — remembering 
that  the  illustration  is  only  a  diagram. 

On  making  a  vertico- lateral  section,  on  the  median  line,  the 
following  parts  are  seen  : 

The  kidney  is  invested  with  a  fibrous  capsule,  which  is  con- 
nected with  the  parenchyma  by  very  delicate  prolongations  of  its 
connective  tissue  fibrillae.  This  capsular  investment  is  in  con- 
nection above  with  the  supra -renal  bodies,  and,  on  the  inner 
border,  with  the  vessels,  etc.,  which  enter  and  leave  the  organ 
at  its  hilum.  The  ureter,  penetrating  the  areolar  tissue  which 
(containing  much  fat)  surrounds  the  hilum,  may,  for  clearness  of 
description,  be  traced  backward  into  the  kidney.  This  tube  ex- 
pands into  the  pelvis,  and  reduplications  of  its  wall  imperfectly 
divide  the  pelvis  into  three  compartments,  or  infimdibula. 

Each  infundibulum  is  subdivided  a^ain,  imperfectly,  into  sev- 
eral pockets  or  calyces;  and  into  each  calyx  may  be  seen,  peeping 
from  the  kidney- substance,  a  papillary  eminence  or  apex  of  a  cone 
—the  pyramids  of  Malpighi.  The  pelvis  is  lined  with  a  variety 
of  transitional  or  imperfectly  stratified  epithelium,  which  will  be 
described  hereafter. 

The  blood-vessels,  lymphatics,  etc.,  pass  in  at  the  hilum,  out- 
side the  ureter,  pelvis,  and  infundibula.  The  artery  divides  into 
numerous  branches,  which  are  seen  in  the  diagram  passing  out- 
ward, between  the  Malpighian  pyramids.  The  renal  vein  pursues 
much  the  same  course,  the  main  trunks  lying  side  by  side. 

On  examining  a  section  of  the  kidney,  made  in  the  direction 
indicated  in  Fig.  115,  a  division  of  an  outer  portion  will  be  mani- 
fest, bounded  externally  by  the  capsule  of  granular  texture,  con- 
taining the  blood-vessels,  etc.  This  is  called  the  cortex.  Within 


THE  KIDNEY 


179 


the  cortical  portion  there  appear  a  number  of  pyramidal  masses—- 
whose apices  we  have  previously  seen — of  finely  striated  texture — 
the  medullary  or  Malpighian  pyramids.  The  cortical  substance 
projects  itself  between  the  pyramids,  completely  isolating  them, 
and  forming  the  cortical  columns  of  Bertini. 

Again  observing  the  outer  cortex,  it  will  present  narrow,  light- 

Capsule  of  the  organ 

Pyramids  of  Ferrein 
Cortical   labyrinths 


Renal     arterial^ 
branches 


Arterial   arcade    branches 


Interlobular     arteries 


FIG.  115.    DIAGRAM  SHOWING  THE  PLAN  OF  STRUCTURE  OF  THE  HUMAN  KIDNEY. 

colored  lines,  which  converge  toward  the  pelvis  ;  and,  eventually, 
pass  into  and  become  a  part  of  the  Malpighian  pyramids.  These 
light  areas,  made  up  of  tubules,  are  the  pyramids  of  Ferrein,  or, 
as  sometimes  called,  the  medullary  rays. 

The  darker  spaces  between  the  pyramids  of  Ferrein  are  called 
labyrinths. 

The  gross  elements,  to  be  understood  before  we  proceed  any 
further,  then,  are .- 


180    '  STUDENTS   HISTOLOGY 

1.  The  capsule  of  the  kidney. 

2.  The  ureter. 

3.  The  pelvis,  with  its  three  infundibula.     The  subdivision  of 
each  infundibulum  into  several  calyces.     Each  calyx  the  site  of  the 
apex  of  a  Malpighian  pyramid. 

4.  The   Mood -vessels  entering  and   leaving   the  hilum.     Their 
subdivision  outside  the  pelvic  lining,  and  final  passage  into  the 
kidney -substance  in  the  cortical  columns. 

5.  Division  of  kidney -substance  into  cortex  and  medullary  or 
Malpighian  pyramids. 

6.  Penetration  of  cortical  tissue  inward  between  pyramids  of 
Malpighi — constituting  the  cortical  columns. 

7.  The  pyramids  of  Ferrein. 

8.  The  labyrinths. 

In  the  domestic  animals  there  are  no  cortical  columns — the 
pyramids  of  Malpighi  coalescing,  as  it  were — thus  presenting  a 
true  medulla. 

We  have  remarked  that  the  kidney  is  made  up  largely  of  urine- 
carrying  vessels  (the  tubuli  uriniferi)  and  blood-vessels.  We  will 
first  study  the  tubular  system,  reserving  for  the  present  the  con- 
sideration of  the  blood-vessel  arrangement. 

THE     TUBULI     URINIFERI 

The  urine -carrying  tubules  commence  in  the  cortex,  and,  after 
taking  a  very  circuitous  route  with  frequently  varying  diameters, 
end  at  the  apex  of  the  pyramids  of  Malpighi,  where  they  pour 
their  contained  urine  into  the  calyces.  The  urine  then  overflows 
into  the  infundibula,  and  is  finally  drained  from  the  pelvis  by 
the  ureter. 

We  shall  begin  with  a  single  typical  tube  ;  and,  understanding 
its  histology,  we  can  build  up  the  organ  by  simply  multiplying 
this  element. 

A  uriniferous  tube,  or  tubule,  commences  in  the  cortex  in  the 
labyrinth  (between  the  pyramids  of  Ferrein),  as  a  thin -walled  sac 
.2  mm.  in  diameter.  This  vesicle,  with  its  contents,  is  a  Mal- 
pighian body  ;  and  its  wall  is  called  the  capsule  of  the  same,  or 
the  ca2)sule  of  Bowman.  The  capsule  consists  of  a  thin  layer  of 
connective  tissue  lined  by  flat  epithelial  cells. 

From  one  side  of  this,  the  expanded  beginning  of  the  tube,  a 
narrow  neck  (25  p*  in  diameter)  is  projected,  which  immediately 


THE  KIDNEY 


181 


widens  (50 /A)  into  a  tube — the  proximal  convoluted  tubule.  This 
tube  (or  this  portion  of  the  tube)  pursues  a  very  tortuous  course, 
always  keeping  between  Ferrein's  pyramids,  and  finally  approaches 
the  base  of  a  Malpighian  pyramid.  Here  it  assumes  an  irregular 
spiral  form — the  spiral  tubule  (42  /*•). 


Afferent  arteriole 
Efferent  arteriole 


Spiral 

Descending  limb  of  Henle's     \ 
loop  ~~~^( 

Ascending    limb 


Henle's  loop 

Collecting     or     straight 
Principal 

Papillary    duct 


FIG.  116.    DIAGRAM  SHOWING  THE  DIVISIONS  OF  A  KIDNEY  TUBULE. 

The  tube  suddenly  narrows  (10  /*),  becomes  straight,  and  passes 
into  a  pyramid  of  Malpighi.  It  reaches  sometimes  just  into  the 
pyramid,  more  frequently,  however,  passing  deeper  than  this — 
often  descending  two -thirds  of  the  distance  to  the  apex;  and  is 
called  the  descending  limb  of  Henle's  loop.  The  descending  limb 
of  Henle's  loop  suddenly  turns  upon  itself,  forming  the  loop  of 


182  STUDENTS  HISTOLOGY 

Henle;  and,  widening  (25  AI),  returns  upon  its  course  as  the 
ascending  limb  of  Henle' s  loop.  It  again  enters  the  cortex, 
keeping  in  a  pyramid  of  Ferrein,  and  passes  outward  until  it 
approaches  the  outer  limit  of  the  cortex,  near  the  capsule  of  the 
kidney.  Here  the  ascending  limb  widens  (50 /A),  forming  the 
distal  convoluted  tubule,  which  pursues  a  tortuous  course  in  the 
outer  cortex.  Many  histologists  also  recognize  an  irregular  tu- 
bule, which  pursues  a  zigzag  course  for  a  short  distance  between 
the  ascending  limb  of  Henle 's  loop  and  the  distal  convoluted  tu- 
bule. "The  distal  convoluted  tubule  then  reenters  a  pyramid  of 
Ferrein,  narrows  (40  /*),  and  passes  a  second  time  into  a  Mal- 
pighian  pyramid,  under  the  title  of  straight  or  collecting  tube,  or 
tube  of  Bellini.  The  last,  after  reaching  very  nearly  to  the  apex 
of  the  pyramid,  unites  with  others  of  a  like  character  to  form  a 
principal  tube  (85/*).  Several  principal  tubes  unite  to  form  a 
papillary  duct  (250/*).  From  one  hundred  to  two  hundred  of 
the  last  open  upon  the  surface  of  the  apical  portion  of  a  Mal- 
pighian  pyramid. 

It  must  be  borne  in  mind  that,  in  describing  the  tubular  sys- 
tem, although  such  terms  as  "convoluted  tube,"  "looped  tube," 
etc.,  are  employed,  these  are  not  separate  tubes,  but  only  names 
applied  to  different  portions  of  one  long  tube.  A  single  tubule, 
as  we  have  seen,  commences  at  Bowman's  capsule,  becomes 
narrowed  like  the  neck  of  a  flask ;  courses  as  the  proximal 
convoluted  and  spiral ;  descends  into,  turns,  and  emerges  from 
a  Malpighian  pyramid,  as  Henle' s  looped  portion  ;  reaches  the 
extreme  cortex,  and  swells  as  the  distal  convoluted ;  and  here 
ends  as  a  single  or  isolated  tubule  and  enters  a  straight  tube. 
The  straight  tubes  receive  several  distal  convoluted  termini,  at 
the  cortical  periphery,  and  pass  in  small  bundles  (forming  the 
pyramids  of  Ferrein)  directly  onward  toward  the  apex  of  a 
Malpighian  pyramid,  uniting  with  one  another  at  very  acute 
angles,  and  the  trunks  formed  by  this  union  uniting  until  the 
tube  terminates  as  a  papillary  duct. 

The  tubes  are  lined  with  epithelial  cells,  and  these  cell -elements 
constitute  the  parenchyma  of  the  kidney.  The  lining  cells  are,  as 
a  rule,  columnar  or  cuboidal.  Two  exceptions  are  presented,  one 
of  which  appears  in  the  flattened  cells  lining  Bowman's  capsule, 
and  the  other  in  the  flattened  cells  of  the  descending  limb  of 
Henle' s  loop.  The  parenchyma  will  receive  attention  in  our 
practical  work. 


THE   KIDNEY 


183 


Capsule 
Stellate      vein 
Interlobular    vein 

Intertiibular  capillarie 
of  Pyramid  of  Ferrein 

Ma Ip ighia n    bodies 

Intertubular  capillaries 
of  Labyrinths 

Interlobular  artery- 
Afferent     vessels 

Efferent    vessels 
Arterial  arcade 

Venous    arcade 
Arteriolce     rectce 

V  enulce     rectce 


Capillaries  of  Malpigliian 
pyramid 

Capillaries   of  papilla 


FIG.    117.    DIAGRAM  SHOWING  THE  ARRANGEMENT  OF  BLOOD-VESSELS  IN  THE 
KIDNEY— AFTER  LUDWIG. 


BLOOD-  VESSELS 

The  vascular  arrangement  is  complex.  The  most  prominent 
and  essential  feature  is  afforded  in  the  existence  of  two  distinct 
capillary  plexuses. 

The  renal  artery,  as  already  described,  sends  branches  into  the 
substance  of  the  kidney.  These  pass  between  the  Malpighian 


184  STUDENTS   HISTOLOGY 

pyramids,  and  in  the  cortical  columns.  These  arterial  trunks  arch 
over  the  bases  of  the  pyramids  of  Malpighi,  forming  the  arterial 
arcade.  From  these  arches  small,  straight  branches  are  sent 
outward  toward  the  capsule  of  the  kidney,  occupying  a  position 
midway  between  the  pyramids  of  Ferrein,  in  the  labyrinths.  The 
last  are  the  interlobular  arteries.  During  their  course,  they  send 
off  side  arteriole  s,  which  penetrate  the  capsule  of  the  Malpighian 
bodies.  Each  afferent  arteriole  breaks  up  into  a  fine  plexus — the 
tuft  or  glomerulus.  The  glomerulus  does  not  entire^  fill  the 
capsule;  so  that  a  space  remains  between  the  spherical  mass  of 
capillaries  and  the  flattened  cells  lining  the  body.  The  glomeruli 
are  enveloped  with  a  single  layer  of  flattened  epithelial  cells. 

The  blood  escapes  from  the  glomerulus  by  a  minute  efferent 
arteriole  which  emerges  from  the  capsule  close  to  the  afferent  ves- 
sel. The  latter  is  the  more  noticeable,  as  it  is  usually  much  the 
larger.  The  efferent  arteriole  immediately  breaks  up  into  a  cap- 
illary plexus,  which  courses  between  the  uriniferous  tubules  of 
the  labyrinths  and  of  the  pyramids  of  Ferrein.  This  plexus  also 
descends  between  the  elements  of  the  pyramids  of  Malpighi. 
From  the  arteries  forming  the  arcade  another  set  of  branches — 
the  arteriolce  rectce — is  given  off,  which,  descending  into  the  Mal- 
pighian pyramids,  provides  another  and  direct  arterial  supply  to 
the  tubular  elements  by  elongated  capillary  loops. 

The  course  of  the  venous  trunks  is  not  unlike  that  pursued  by 
the  arteries.  Interlobular  veins,  lying  in  the  cortical  labyrinths 
parallel  with  and  close  to  the  arteries,  pass  into  a  venous  arcade. 
In  the  medulla  the  venous  blood  is  collected  from  the  capillaries 
and  carried  to  the  bases  of  the  Malpighian  pyramids  in  small 
veins — venulce  rectce.  The  blood  from  the  cortical  intertubular 
capillaries  is  collected  in  the  interlobular  veins. 

A  peculiar  vascular  arrangement  exists  just  beneath  the  cap- 
sule of  the  kidney,  consisting  of  scattered  venous  plexuses,  the 
venoe  stellatce.  They  contain  blood  collected  from  contiguous 
intertubular  capillaries,  and  are  in  connection  with  the  summits  of 
the  interlobular  veins. 

From  what  has  been  said,  it  will  be  seen  that  the  cortical  and 
medullary  blood -supplies  are,  to  a  certain  extent,  independent  of 
each  other.  The  arteriolaB  rectae  provide  a  vascular  supply  to  the 
elements  of  the  Malpighian  pyramids  even  after  many  of  the 
glomeruli  have  become  obliterated  by  disease. 

Nerve  and  lymphatic  elements  are  not  very  prominent  features 


THE   KIDNEY  185 

in  sections  of  the  kidney.  Small  non-medullated  nerve -trunks 
may  be  demonstrated  in  transverse  sections  of  the  cortex,  espe- 
cially near  the  bases  of  the  medullary  pyramids,  where  they  will 
be  seen  in  company  with  the  blood-vessels  of  the  arcades.  Lymph- 
channels  are  also  to  be  seen  in  the  vicinity  of  the  vessels  of  the~ 
hilum,  and  in  the  connective  tissue  of  the  capsule. 

The  histology  of  the  kidney  will  be  comprehended  better  by  a 
reference  to  its  function.  The  separation  from  the  blood  of  a 
quantity  of  water,  together  with  certain  excremeiititious  matters, 
is  effected,  partly  in  the  Malpighian  bodies,  and  partly  in  the 
tubules.  The  vascular  tuft — the  glomerulus — is  covered  with  a 
close -fitting  membrane  composed  of  flat  cells.  The  blood  in  this 
plexus  parts  with  a  certain  amount  of  its  water,  which  passes 
through  the  walls  of  the  capillaries  and  through  the  cells  m covering 
them.  Whether  this  be  due  to  osmosis  or  to  some  selective  power 
of  the  cells  we  have  no  concern — suffice  it  to  say  that  certain  salts 
afterward  appearing  in  the  urine  do  not  leave  the  blood  at  this 
point.  The  efferent  glomerular  arteriole,  it  will  be  remembered, 
breaks  into  a  capillary  plexus,  which  brings  the  blood  close  to  the 
walls  of  the  convoluted  tubules.  It  is  believed  that  the  cells  lining 
these  tubules  select  from  the  blood  circulating  in  the  contiguous 
capillaries  such  effete  materials  as  escaped  elimination  from  the 
glomeruli. 

Moreover,  it  seems  that  some  of  the  water  which  escaped 
in  the  first  instance  and  entered  the  proximal  convoluted  tubules, 
is  here  returned  to  the  blood  by  the  intervention  of  the  same 
tubular  lining  cells  which  excrete  the  salts.  Without  referring 
to  any  further  work  done  by  the  kidney,  it  is  important  to 
understand  this  part  of  the  structural  scheme :  That  the  first  part 
of  the  uriniferous  tubule  is  the  prominent  excreting  part.  That 
the  latter  portion  of  the  tubule — the  portion  in  the  Malpighian 
pyramids,  the  straight  tubule — is  for  the  collection  and  drainage  of 
the  urine  already  excreted.  And  that  between  the  excreting  first  part 
and  the  draining  second  part,  there  exists  a  narrow  looped  tubule — 
the  loop  of  Henle.  The  effect  of  this  narrowing  and  tortuosity  of 
the  tubule  will  be  to  present  a  resistance  to  the  outflow  of  urine 
from  the  proximal  portion  of  the  tubule.  The  diluted  urine, 
excreted  in  the  Malpighian  bodies,  is  held  back  for  a  while  in 
the  proximal  convoluted  tubule,  and  time  given  for  the  comple- 
tion and  perfection  of  the  excretory  processes  by  the  tubular 
parenchyma. 


186 


STUDENTS   HISTOLOGY 


PRACTICAL    DEMONSTRATION 

The  human  kidney  is  rarely  found  in  a  perfectly  normal  condition.  The 
demonstration  can  be  made  from  the  kidney  of  the  pig,  except  as  regards 
certain  features.  The  medullary  pyramids  do  not  exist  in  the  domestic  ani- 
mals, and  the  parenchyma  presents  very  essential  differences  from  the  cells  of 
the  human  kidney.  Still,  very  much  can  be  learned  from  the  organ  of  the  pig, 
dog,  or  rabbit.  The  tissue  should  be  divided  so  as  to  permit  sections  to  be 
made  parallel  with  the  medulla,  and  to  include  both  it  and  the  cortex.  The 
hardening  is  best  by  Miiller's  fluid.  Small  pieces  hardened  quickly  in  strong 
alcohol,  however,  stain  very  finely  with  heematoxylin  and  eosin.  Sections  of 
.kidneys  the  blood-vessels  of  which  have  been  injected  should  also  be  studied. 


,Fio.  118.    SECTION  OF  HUMAN  KIDNEY,  CUT  PARALLEL  TO  THE  PYRAMIDS  OF  FERREIN. 
SHOWING  THE  CORTEX  AND  PART  OF  A  MALPIGHIAN  PYRAMID  (X  30). 

A,  A.  Capsule  of  kidney. 

B,  B.  Pyramids  of  Ferrein. 

C,  C.    Cortical  labyrinths. 

D,  D.  Malpighian  bodies.    Many  of  the  glomeruli  drop  out  in  the  course  of  preparation,  and 
such  empty  capsules  of  Bowman  appear  as  light  circular  spots. 

E,  E.  Interlobular  arteries. 

F,  F.   Boundary  region. 

G,  G.  Transverse  sections  of  vessels  of  the  arcades. 
H.  Base  of  a  Malpighian  pyramid. 


THE  KIDNEY  187 


HUMAN   KIDNEY.      SECTION   PARALLEL  WITH   MALPIGHIAN   PYRAMID. 
STAINED   WITH   H^EMATOXYLIN  AND   EOSIN 

OBSERVE:  (Kg.  us) 

(Naked  eye,) 

1.  The  thickness  of  the  cortex,  and  its  granular  appearance 
as  compared  with  the  medullary  portion. 

2.  The  markings  of  the  cortex.     (These  consist  of  alternating 
light  and  dark  lines,  radiating  from  the  bases  of  the  Malpighian 
pyramids.     The  lighter  masses  consist  largely  of  collecting  tubes, 
together  with  ascending  limbs  of  Henle's  looped  tubes — otherwise 
called   medullary  rays.      Between   these   lighter   areas    the    dark 
labyrinths  appear,  in  which,  by  careful  attention,  the  Malpighian 
bodies  may  be  made  out  as  minute  red  dots.) 

3.  A  region  just  outside  the  medullary  pyramids — not  as  well 
marked  as  the  outer  cortex,  in  which  few  Malpighian  bodies  are 
seen — the  boundary  region. 

4.  The   finely   striated    medullary   or    Malpighian    pyramids. 
(The  section  will  usually  include  portions  of  two  of  the  last.) 

5.  That  the  bases  of  the  pyramids  do  not  appear  as  a  sharply 
defined  line,  but  fade  into  the  boundary  region;   while  the  union  of 
the  latter  with  the  cortex  proper  is  equally  ill  defined. 

(L.)     Fig.  118. 

1.  The  cortical  labyrinths,  in  which  search  for — 

a.  Portions  of  the  interlobular  arteries,  together  with  the 
smaller  twigs  of  the  arterial  arcade. 

1).  The  Malpighian  bodies.  (The  tuft  or  glomerulus  which, 
with  this  power,  appears  as  a  granular  mass,  is  wanting  in  numer- 
ous places,  as  indicated  by  the  empty  capsules.) 

c.  The  remaining  area  occupied  largely  by  the  convoluted 
tubes,  proximal  and  distal. 

2.  The  pyramids  of  Ferrein.     (Observe  that,  as  they  pass  into 
the  pyramids  of  Malpighi,  they  are  well  defined,  but  that  they  are 
lost  as  they  approach  the  region  of  the  capsule.) 

(H.)     Fig.  119. 

1.  Malpighian  body.  (Select,  after  searching  several  fields,  a 
specimen  which  shows  either  the  afferent  or  efferent  vessel  of  the 
glomerulus.  It  will  be  very  difficult  to  find  a  capsule  connected 
with  the  neck  of  a  proximal  convoluted  tube,  as  it  rarely 


188 


STUDENTS   HISTOLOGY 


happens  to  be  so  sectioned.     One  may  indeed  be  obliged  to  examine 
a  dozen  slides  before  succeeding.)     Note — 

a.  The  capsule  (of  Bowman  or  of  Miiller) .     (Observe  its  thick- 
ness, as  this  becomes  important  in  connection  with  the  pathology 
of  the  kidney.) 

b.  The  flattened  cells  lining  the  capsule.     (Many  of  them  will 
have  become  detached  in  the  preparation  of  the  section.) 


FIG.  119. 


PART  OF  THE  CORTEX  OF  HUMAN  KIDNEY.     HIGH-POWER. 
SPECIMEN  AS  FIG.  118  (X  400). 


SAME 


A.  Ascending  limb  of  Henle's  loop. 

B.  Collecting  tubule — longitudinal  section. 

C.  Collecting  tubnle.    The  upper  part  of  the  tube  is  not  sectioned,  but  shows  the  attached 
bases  of  the  lining  cells,  and  thus  simulates  pavement  epithelium.    A,  B,  and  C  are  in  a  pyramid 
of  Ferrein. 

D.  Capsule  of  a  Malpighian  body.    The  emerging  tubule  is  not  shown,  as  the  body  is  in  T.  S. 

E.  Flattened  lining  cells  of  D. 

F.  Glomerulus. 

G.  Efferent  arterioles. 
H.  Afferent  arteriole. 
I.    Convoluted  tubules. 

J.    Ascending  limb  of  Henle's  loop. 
K.  Intertubular  capillaries. 

c.  The  glomerulus.     (The  great  number  of  nuclei  obscures  the 
loops  of  capillaries.    Remember  that  the  nuclei  belong  partly  to  the 


THE   KIDNEY  189 

vessels  and  partly  to  the  flattened  cells  covering  the  glomerulus. 
Endeavor  to  find  transversely  divided  loops  of  the  vessels,  show- 
ing blood  within.) 

d.  That  the  glomerulus  does  not  entirely  fill  the  capsule. 

e.  That  the  glomerulus  is  frequently  divided. 

/.  That  the  glomerulus  is  usually  in  contact  with  the  capsule 
at  some  one  point,  where  search  may  be  made  for 

y.  The  afferent  and  efferent  arterioles.  (The  afferent  is  more 
frequently  demonstrable,  and  may  be  differentiated  by  its  large 
size,  and  the  connection,  which  can  often  be  traced,  with  the  inter- 
lobular  artery.) 

2.  Convoluted   tubules.      (The  convoluted  tubules  found  just 
beneath  the  capsule  of  the  kidney  generally  belong  to  the  distal 
variety,  and  they  are  not  as   favorable  specimens  as  the  deeper 
proximal  portions,  on  account  of  the  crowding  of  the  tubular  ele- 
ments in  the  outer  cortical  regions.     Select  a  transverse  section 
and  observe : ) 

a.  The  thin  membrana  propria,  or  wall  of  the  tube.  (It  does 
not  appear  to  be  made  up  of  fibrillated  connective  tissue,  but  .has 
a  rather  homogeneous  structure.  Nuclei,  however >  may  occasionally 
be  seen,  which  apparently  belong  to  this  tissue.) 

1).  The  peculiar  lining  cells.  (They  are  unlike  any  other 
parenchymatous  elements  found  in  the  body.  Note  that,  while 
they  are  evidently  of  the  columnar  or  cylindrical  type,  they  differ 
greatly  in  form  and  size.  The  protoplasm  is  hazy,  granular,  and 
frequently  striated.  They  take  a  dirty  brick -red  hue  from  the 
eosin.) 

c.  The  lumen.  (Compared  with  the  diameter  of  the  tube- wall, 
the  lumen  is  very  small,  and  presents  a  stellate  figure.  The  urine, 
in  passing  through  the  tubule,  is,  consequently,  brought  in  contact 
with  a  very  considerable  portion  of  the  lining. ) 

3.  The  large  proportion  of  the  cortical  area  occupied  by  the 
convoluted  tubules,  and  the  exceedingly  small  amount  of  inter- 
tubular  connective  tissue. 

4.  The  intertubular  capillaries.     (These  are  exceedingly  small 
and  difficult  of  demonstration  unless  filled  with  blood.     The  nuclei 
of  the  endothelial  wall  are  frequently  seen.     The  cells  of  the  con- 
voluted tubules  are  not  infrequently  detached  from  the  membrana 
propria,  and  the  space  so  formed  may  be  mistaken  by  the  careless 
observer  for  longitudinal  sections  of  capillaries.     These  vessels  are 
much  better  seen  in  an  injected  kidney;   although  if  ,an  organ  be 


190  STUDENTS    HISTOLOGY 

selected  containing  considerable  blood,  and  the  corpuscular  ele- 
ments have  their  color  preserved  [as  in  bichromate  hardening] ,  the 
vessels  will  be  easily  demonstrated.) 

5.  Ascending  limb  of  Henle's  loops  in  the  cortical  labyrinths. 
(The  general  course  of  these  tubules  is  confined  to  the  pyramids 
of  Malpighi  and  Ferrein;  but  occasionally  one  of  them  may  be 
seen  passing  in  a  tortuous  course  toward  the  outer  cortex,  running 
between  the  proximal  convoluted  elements.  They  are  easily  recog- 
nized by  their  small  size  and  relatively  large  lumen.  They  are 
lined  with  short  columnar  or  cuboid  cells,  which  stain  deeply 
blue  with  the  haematoxylin . ) 

G.  The  pyramids  of  Ferrein. 

a.  Collecting  tubes.  (These  will  generally  be  recognized  by 
their  large  size  and  the  blue  color  of  the  staining.  They  are  lined 
with  columnar  cells,  which  are  hexagonal  in  transverse  section; 
and  this  gives  an  appearance  like  pavement  epithelium  when  they 
are  seen  from  above  or  below.  Endeavor  to  find  a  tube  split 
through  the  center  longitudinally,  and  note  the  typical  columnar 
cells,  as  they  project  inward  from  the  membrana  propria  toward 
the  now  open  lumen.) 

1).  The  spiral  tubules.  (These  resemble  somewhat  the  convo- 
luted tubules,  especially  as  their  cells  take  much  the  same  dirty  red 
color.  The  cells,  however,  plainly  columnar,  are  large  and  hexag- 
onal in  transverse  section.  The  lumen  is  small.) 

c.  Ascending  limbs  of  Henle's  loop.     (These  are  small  tubes, 
and  have  already  been  described. ) 

d.  The  intertubular   capillaries.     (Inasmuch  as,  in   the  speci- 
men under  consideration,  the  vessels  of  the  pyramids  are  mostly  in 
tran verse  section,  they  are  not  readily  made  out,  especially  if  the 
blood-corpuscles  have  become  decolorized. 

7.  Elements  of  the  medullary  portion.     Fig.  120. 

a.  Collecting  tubes.  (These  tubes  constitute  a  large  propor- 
tion of  the  medulla  of  the  organ.  They  have  already  been 
described.  As  the  apex  of  the  Malpighian  pyramid  is  approached, 
and  the  straight  tubules  unite  to  form  the  principal  collecting 
tubes,  these  again  uniting  to  form  the  papillary  ducts,  the  lining 
cells  will  be  seen  to  get  shorter  and  the  lumina  larger. ) 

6  Spiral  tubes.  (These  can,  in  many  instances,  be  followed 
down  from  the  pyramids  of  Ferrein;  and  examples  are  frequently 
seen  very  near  the  pelvis  of  the  kidney  in  the  cortical  columns.) 

c.  Descending  limbs  of  Henle's  loop.     (These  tubes  are  the 


THE   KIDNEY 


191 


most  difficult  of  all  the  tubuli  uriniferi  to  demonstrate.  The 
section  must  be  very  thin,  and  even  then  they  may  be  mistaken 
for  blood -capillaries.  Their  peculiar  feature  consists  in  the  wavy 
lumen,  which  is  produced  by  the  alternate  disposition  of  the  lining 
cells.) 

d.  Loops  of   Henle.     (The  loops  will   be  recognized   by  the 
curving  of  the  tube.      They  are  lined  with  short  columnar  cells, 


FIG.  120.    MEDULLARY  PORTION  OF  SPECIMEN  SHOWN  IN  FIG.  118  (X400). 

A.  Collecting  tubule  in  L.  S. 

B.  Collecting  tubule  from  above,  showing  attached  bases  of  lining  cells. 

C.  Collecting  tubule  presenting  different  appearance  of  lining  cells,  according  to  mode  of 

section. 

D.  Ascending  limb  of  Henle's  loop. 

E.  Same  as  last.    The  upper  end  of  the  tubule  not  sectioned. 

F.  Descending  limb  of  Henle's  loop.    Below  may  be  seen  the  loop  and  ascending  limb. 

G.  Oblique  section  of  large  collecting  tubule. 

H.  Basal  attached  extremities  of  cells  lining  a  large  collecting  tubule. 
I.    Intertubular  capillaries. 

which  are  sharply  brought  out  by  the  haematoxylin.     On  account 
of  their  course,  but  few  complete  sections  are  seen.) 

e.  Ascending  limbs.     (Conveniently  traced  from  the  loops.) 
/.  Intertubular  blood-vessels.     (Do  not  mistake  tubules  con- 


192  STUDENTS   HISTOLOGY 

taining  blood  for  capillaries.  The  human  kidney  is  rarely  abso- 
lutely normal;  and  blood  is  frequently  found  outside  the  proper 
channels.  The  vessels  will  be  differentiated  by  the  histology  of 
their  walls.  Quite  a  number  of  venules  will  be  seen  running  in 
groups  in  the  medulla — the  venulce  rectce. 

8.  The  same  elements  as  in  7  (shown  in  a  transverse  section 
of  the  middle  of  a  Malpighian  pyramid,  Fig.  121). 


FIG.    121.     TRANSVERSE    SECTION    OF    PYRAMID    OF    MALPIGHI.      SAME    TISSUE    AS 
SHOWN  IN  FIG.  118.     STAINED  WITH  H^EMATOXYLIN  AND  EOSIN  (X400). 

A.  Group  of  intertubular  blood-vessels. 

B.  Collecting— straight— tubules. 

C.  Descending  limb  of  Henle's  loop. 

D.  Ascending  limb  of  Henle's  loop. 

E.  Principal— collecting— tubule. 

F.  Principal  tubule.    Lower  portion  near  the  papillary  duct. 

The  ring  of  cells  will  be  seen  detached  from  the  membrana  propria  in  some  instances.     This 
is  due  to  contraction  of  the  tissue  during  the  hardening. 

In  amphibians  the  epithelial  cells  at  the  neck  of  the  capsule  of 
Bowman  are  ciliated.  In  man  and  the  mammals  the  epithelial  cells 
of  the  convoluted,  spiral,  and  irregular  tubules  and  the  ascending 
limb  of  Henle's  loop  have  distinct,  vertical  striations  close  to  the 
basement  membrane.  The  cells  of  the  convoluted  tubules  show 


PELVIS  OF  THE  KIDNEY  AND    URETER  193 

variations  in  size  and  in  the  number   of  granules,   dependent  on 
the  state  of  secretion. 

DIAGRAM   SHOWING   DISTRIBUTION   OP   TUBULES   (AFTER   PIERSOL) 

CORTEX. 
Labyrinth.  Medullary  Ray. 

Malpighian  bodies.  Spiral  tubules. 

Necks  of  the  tubules.  Ascending  limbs  of   loops  of 

Proximal  convoluted  tubules.  Henle. 

Irregular  tubules.  Collecting  tubules. 

Distal  convoluted  tubules. 

Collecting  tubules. 

Loops  of  Henle. 

Descending  limbs. 

V   MEDULLA. 
Ascending  limbs. 

Collecting  tubules. 


PELVIS    OF    THE    KIDNEY   AND    URETER 

The  coats  of  the  ureter  are  three  in  number — mucous,  muscu- 
lar, and  fibrous.  The  muscle  is  unstriated,  and  is  divided  into 
inner  longitudinal  and  outer  circular  layers.  The  pelvis  of 
the  kidney,  and  the  calyces  and  infundibula  present  a  similar 
structure.  The  circular  muscular  fibers  are  numerous  around  the 
papillae,  and  form  a  kind  of  sphincter. 

Obtain  the  ureter  of  a  human  subject,  if  possible.  Fix  the  fresh  ureter 
with  alcohol  or  Miiller's  fluid.  Imbed  in  celloidin  or  paraffin.  Cut  thin  sec- 
tions, stain  with  hsematoxylin  and  eosin,  and  mount  as  usual. 

OBSERVE  : 
(L.) 

1.  The  relative  thickness  of  the  epithelium. 

2.  The  narrow  mucosa. 

3.  The  internal  longitudinal  muscular  layer. 

4.  The  bundles  of  the  external  circular  muscular  layer. 

5.  The  arteries  between  the  muscular  bundles. 

6.  Adipose  tissue,  more  or  less  abundant  in  the  loose  cellular 
tissue   surrounding    these   canals.     (This    element   will    afford   a 
prominent  feature  of  the  section  of  the  pelvis  of  the  kidney,  while 
the  muscular  tissue  will  be  seen  to  a  limited  extent  only.) 

(H.)     Fig.  122. 

7.  The  epithelium,     (a)  That  it  is  of  the  thin,  stratified  squa- 
mous  type  known  as  transitional.    >(&)  The  broad  basal  attach- 
ed 


194 


STUDENTS   HISTOLOGY 


ment  of  the  deep  cells,  (c)  The  elongated  form  of  the  cells 
generally,  (d)  The  more  flattened  surface  cells,  (e)  The  out- 
line of  the  last,  as  seen  in  the  detached  specimens.  (/)  The  deeper 
cells  present  tapering  prolongations,  generally  at  one  end  only, 


FIG.  122.  SECTION  OF  THE  URETER  NEAR  THE  PELVIS  OF  THE  KIDNEY.  STAINED 

WITH   ILEMATOXYLIN   AND   EOSIN     (X400). 

A.  Rich  capillary  plexus  of  the  mucosa. 

B.  Internal  muscular  coat. 

C.  External  muscular  coat. 

D.  Large  vessels  of  the  areolar  adventitia. 

E.  Deep  layer  of  somewhat  cubical  cells. 

F.  "Tailed  cells"  of  the  middle  epithelial  layers. 

G.  Surface  cells  in  profile. 
H.  Detached  surface  cells. 

and  are  hence  called  "tailed  cells."     They  may  be  confounded  with 
similarly  shaped  cells  from  the  bladder. 


THE     URINARY    BLADDER. 

The  layers  of  the  bladder  are  mucous,  muscular,  and  fibrous, 
while  part  of  it  has  a  serous  covering  derived  from  the  peritoneum. 
The  muscle  is  unstriated,  and  is  arranged  in  inner  and  outer  longi- 


THE    URINARY  BLADDER 


195 


tudinal  layers,  with  a  circular  layer  between  them.  The  muscular 
layers  are  not  well  marked.  The  internal  vesical  sphincter  is 
formed  from  an  increase  in  the  thickness  of  the  circular  layer. 
Numerous  minute  ganglia  are  found  along  the  nerves  of  the  blad- 


FIG.   123.    VERTICAL    SECTION  OP  THE   LINING  PORTION  OF  THE  BLADDER  (MALE) 
BEHIND  THE  TRIGONE.    STAINED  WITH  ELEMATOXYLIN  AND  EOSIN   (X400). 

A.  Connective  tissue  of  sub-epithelial  region. 

B.  Capillary  supply  of  sub-epithelial  region. 

C.  Muscular  wall  of  bladder. 

D.  Deep  cells  of  the  epithelial  lining. 

E.  Middle  region  of  lining. 

F.  Detached  surface  cells,  showing  processes  beneath. 

G.  Thin  surface  cells  in  profile. 

H.   Squamous  surface  cells,  seen  detached,  in  plan. 
I.     Vacuolated  cells. 

der,  which  contain  both  medullated  and  non-medullated  fibers. 
As  in  the  ureter,  the  blood  supply  of  the  mucous  and  muscular 
coats  is  abundant.  Small  nodules  of  lymphoid  tissue  occur  in 
the  mucous  membrane.  The  epithelium  is  transitional ;  but  the 
disposition  of  the  cells  varies  with  the  extent  to  which  the  bladder 
is  expanded. 

Prepare  sections  of  human  bladder  in  the  same  manner  as  sections  were 
made  of  the  ureter. 


196  STUDENTS  HISTOLOGY 

OBSERVE  : 
(L.) 

1.  The    epithelial    lining,     (a)  That   it   is  formed    after    the 
transitional  type. 

2.  The  mucosa  and  its  capillary  supply. 

3.  The  dense  muscular  portion. 

(H.)     Fig.  123. 

4.  The  epithelium,     (a)  The  size  of  the  cells.     (&)   The  layers 
of  the  epithelium,  which  are  deep,  middle,  and  superficial,     (c) 
That  the  deep  cells  are  polyhedral  or  columnar,     (d)   The  form  of 
the  middle  cells  ;   not  unlike  those  of  the  corresponding  region  in 
the  ureter,     (e)  The  large,  scaly  surface  epithelial  cells.     (Note 
that   while  these  all  appear  flat,   when  seen  in  plan,   it   is  only 
those   of   the  extreme  surface   that   are   simple   scales ;    the   less 
superficial  examples  show,  when  viewed  in  profile,  prolongations 
from  the  under  surface,  by  means  of  which  union  is  effected  with 
the  deeper  cells.) 

THE    URETHRA 

The  urethra  consists  of  a  mucous  coat  surrounded  by  muscular 
and  fibrous  tissue.  The  muscle  is  unstriated.  Numerous  papilla 
cover  the  surface  of  the  mucous  membrane  proper.  The  lining  in 
the  female  urethra  is  stratified  squamous  epithelium.  A  few  small 
glands  are  found  in  the  female  urethra.  The  lining  of  the  male 
urethra  varies  in  the  different  regions.  In  the  prostatic  region  it 
is  transitional  epithelium ,  as  in  the  bladder ;  in  the  membranous 
portion  it  is  stratified  columnar ;  in  the  spongy  or  penile  it  is 
simple  columnar ;  while  in  the  fossa  navicularis  it  becomes  strati- 
fied squamous  epithelium,  and  is  continuous  with  that  covering 
the  glans  penis.  Small,  branched,  mucous  glands  (the  glands  of 
Littre)  occur  throughout  the  male  urethra. 


THE    FEMALE   GENERATIVE    ORGANS  197 

THE  FEMALE  GENERATIVE  ORGANS 

THE    VAGINA    AND    UTERUS 


The  walls  of  the  vagina  are  lined  with  a  mucous  membrane, 
covered  with  a  thick,  stratified  squamous  epithelium,  beneath  which 
are  numerous  papillae.  The  submucous,  unstriated  muscular,  and 
fibrous  adventitious  coats  are  not  well  defined.  Glands  are  not 
present. 

The  uterus  has  mucous,  muscular,  and  serous  layers,  but  the 
muscular  layer  is  much  the  thickest.  The  muscle  is  unstriated. 
The  fibers  increase  both  in  size  and  number  during  pregnancy. 
The  mucous  membrane  is  covered  with  a  single  layer  of  columnar, 
ciliated  epithelial  cells,  which  create  a  current  in  the  direction  of 
the  cervix.  Numerous  tubular  glands,  lined  with  similar  cells, 
extend  down  to  the  muscular  layer.  During  menstruation  the 
mucous  membrane,  having  become  thickened,  soft,  and  distended 
with  blood,  undergoes  disintegration  in  its  outer  portion,  which  is 
cast  off.  Accompanying  this  phenomenon  there  is  an  escape  of 
blood  from  the  capillaries.  The  epithelium  is  quickly  renewed 
from  the  deeper  portions  of  the  glands  of  the  mucous  membrane. 


PRACTICAL    DEMONSTRATION 

From  the  body  of  a  (preferably  young)  human  female,  as  soon  as  possi-" 
ble    after  death,   remove  centimeter  cubes  of  the  organs  required,   observing 
that  the  lining  is  included.      The  outer  portions  are  of  very  little  moment 
comparatively.     Secure  pieces  from  the  os,  cervix,  and  fundus  of  the  uterus, 
and  the  wall  of  the  vagina. 

The  vagina  and  uterus  of  a  human  subject  should  be  secured,  because 
their  structure  differs  considerably  from  that  of  the  same  organs  in  the  lower 
animals.  The  differences  are  greater  than  is  the  case  with  many  of  the 
organs  hitherto  studied. 

We  desire  to  prepare  the  tissue  so  as  to  keep  the  original  form  of  cell- 
elements — to  avoid  contraction — and  Miiller's  fluid  will  accomplish  this  per- 
fectly. Allow  the  pieces  to  remain  for  a  month  in  the  bichromate  solution, 
with  an  occasional  change.  Complete  the  hardening  in  alcohol,  after  washing 
as  usual.  Infiltrate  with  celloidin,  and  let  the  sections  be  vertical  to  the 
mucous  surface.  The  tissues  should  not  be  handled  with  the  fingers  ;  other- 
wise the  epithelial  lining  cells  will  be  detached.  Stain  with  haematoxylin  and 
eosin;  mount  in  balsam. 


198 


STUDENTS    HISTOLOGY 


VAGINA  AND  UTERUS  OF  THE  HUMAN  FEMALE  AT  PUBERTY — VER- 
TICAL DEXTRO-SINISTRAL  SECTION  OF  THE  RIGHT  LIP  OF  THE 
OS,  AND  INCLUDING  PART  OF  THE  VAGINAL  CUL-DE-SAC 

OBSERVE  : 
(L.) 

1.  The  outline  of  the  section.     (Commencing  at  D,  Fig.  124, 
which  is  placed   in  the  internal  os,  follow  downward,  out  upon 


FIG.  124.  VERTICAL  DEXTRO-SINISTRAL  SECTION  OF  THE  RIGHT-HAND  SIDE  OF  THE 
Os  UTERI.  SHOWING  THE  INTERNAL  Os,  THE  EXTERNAL  Os,  THE  VAGINAL 
CUL-DE-SAC,  AND  THE  UPPER  PORTION  OF  THE  VAGINAL  WALL  (X  60). 

A.  The  letter  is  placed  in  the  internal  os. 

B.  Vaginal  cul-de-sac. 

C.  Vaginal  wall. 

D.  Columnar  epithelium  of  the  internal  os.    In  the  upper  portion  the  tubular 

glands  are  well  seen. 

E.  Stratified  epithelium  of  the  vaginal  lining. 

F.  Change  at  the  external  os  from  stratified  flattened  to  columnar  epithelium. 


the  external  os,  curve  upward,  reaching,  at  B,  the  vaginal  cul- 
de-sac.     Descend  along  the  right  vaginal  wall.) 

2.  The     irregular     surface     of     the     internal     uterine    wall. 
(Caused  by  longitudinal  section  of  the  glandulee  uterinae  or  glan- 


VAGINA  AND    UTERUS  199 

dulae  utriculares— branched  tubular  glands.  These  are  increased 
in  depth  during  pregnancy,  and  are  most  prominent  in  the  lower 
portion  of  the  organ.) 

3.  The  epithelium,     (a)  The  deeply  stained  layer,  lining  of 
the  vagina,  cul-de-sac,  and  external  os.     (b)  The  wavy  course 
of  a  as  it  covers  the  irregularly  formed  and  often  imperfect  pa- 
pillae of  the  mucosa.     (c)   The  lighter  appearance  of  the  lining 
of  the  internal  os.      (d)   Projection  of  the  last  into  the  glands. 
(e)   The    sharp    line    of    separation  between  the    deeply  stained 
lining  common  to  the  vagina  and  the  lighter  lining  of  the  uterus 
at  the  external  os  (Fig.  124,  F). 

4.  The  mucosa  of  the  uterus.     (There  are  no  sharply  denned 
regions  in  the  genito- urinary  tract  corresponding  to  the  mucosa 
and  submucosa  of  typical  mucous  membranes.     The  arrangement 
generally  is,    (1)   an  epithelial  lining;     (2)   a  subepithelial  struc- 
ture, consisting  of  a  more  or  less  prominent  or  abundant  plexus 
of  capillaries  supported  by  delicate  connective  tissue,  and  which 
corresponds    to    the    typical    mucosa;     (3)    the    muscular   walls 
proper,   consisting   of    layers    in    different    directions,    frequently 
irregularly  disposed  and  seldom  in  distinct  fasciculi.) 

5.  The  mucosa  of  the  vagina   (the  surface  of  which  is  beset 
with  small  papillae,  and  in  which  large  veins  are  prominent) . 

6.  The    uterine     and    vaginal    walls    (consisting    largely    of 
involuntary   muscular   fibrils,    recognized   by   the   elongated   and 
deeply  stained  nuclei,  and  containing  numerous  thick -walled  ar- 
teries and  irregular  lymph -spaces.) 

(H.) 

7.  The  uterine  epithelium  (Fig.    125).     (a)  That  it  consists 
of  a  single  layer  of  cells.      (&)   That  the   cells  are   columnar  or 
cylindrical,     (c)    The  cells  in  transverse   section  are   polygonal. 
(d)  They  are  ciliated.   (If  the  section  has  been  properly  prepared 
from   uninjured  tissue,   the  cilia  will   be  seen  without  difficulty, 
and  especially  in  the  depressions  where  they  are  somewhat  pro- 
tected.)     (e)   The  cell-body  and  nucleus.      (Note  the  elongated, 
clear,  free  portion,  and  the  frequent  curving  of  the  whole.     Near 
the  attached   extremities,   which   often  appear  pointed,  note   the 
small,    deeply    stained   nuclei.)      (/)   The    large    mucous    crypts 
which  occur  in  the  cervix.     Retention  of  their  secretion  produces 
the  cysts  which  are  known  as  the  ovula  Nabothi.      (g)  It  is  dif- 
ficult to  see  the  basement  membrane. 


200 


STUDENTS    HISTOLOGY 


8.  The  abrupt  transition  from  columnar  to  flattened  cells  in 
the  epithelium  of  the  external  os.      (a)  The   shortening  of   the 
columnar  cells  as  the  point  of  change  is  approached.      (Sections 
must  be  examined  until  one  is  found  showing  this  point  well.     The 
illustration  [Fig.  125]  is  not  exaggerated,  and  a  properly  cut  and 
selected  specimen  must  exhibit  clearly  the  last  columnar  and  the 
adjoining  flattened  cell.) 

9.  The  vaginal  epithelium  (Figs.  125  and  126).     (a)  That  it  is 


FIG.  125.    EXTERNAL  Os  OF  FIG.  124.    MORE  HIGHLY  MAGNIFIED  (X400). 

A.  Muscular  tissue  of  the  os  uteri,  with  numerous  blood-vessels. 

B.  Capillary  plexuses  of  subepithelial  tissue— mucosa. 

C.  Ciliated  columnar  cells  covering  the  os. 

D.  Vacuolated  cells. 

E.  Shortening  of  the  columnar  cells  preparatory  to 

F.  Change  from  typical  uterine   epithelium— ciliated  columnar  cells— to  flattened 

stratified  cells. 

G.  Papillary  structure  of  the  niucosa  of  the  external  os,  after  change  of  epithelium. 

of  the  stratified  squamous  variety,  (b)  The  deepest  line  of  cells 
following  the  sinuous  line  formed  by  sectioning  the  papillary  mucosa. 
(c)  That  the  cells  are  more  or  less  flattened.  (d)  That  their 
edges,  excepting  those  of  the  surface,  are  serrated,  (e)  The 


VAGINA    AND    UTERUS 


201 


change  in  form  as  the  surface  is  approached.  (/)  The  surface 
cells.  (These  are  very  much  flattened,  and  so  fused  in  longitudinal 
section  as  to  resemble  fibers.)  (g)  Detached  surface  cells.  (At 
H,  Fig.  126,  these  are  shown  in  plan,  having  been  torn  off;  those_ 
intact  are,  of  course,  seen  in  profile.)  (h)  The  nuclei,  evenly 
granular,  usually  larger  than  a  red  blood -corpuscle. 

10.  The  subepithelial  vaginal   structures.      (a)  The  large  and 
abundant  capillaries  of   the  rnucosa.     (b)   The    submucosa,  not 


FIG.  126.     VERTICAL  SECTION  OF  THE  VAGINAL  LINING  AT  PUBERTY. 
STAINED  WITH  H^MATOXYLIN  AND  EOSIN  (X  400). 

A.  Subepithelial  capillary  plexus. 

B.  Papillary  arrangement  of  the  mucosa. 

C.  Large  blood-vessels  in  the  submucosa. 
I).  Muscular  wall  of  vagina. 

E.  Deep  cells  of  the  lining  epithelium. 

F.  Middle  strata  of  lining  stellate  cells. 

G.  Surface  cells  in  profile. 

H.  Surface  cells  in  plan — detached. 


clearly  separated  from  the  mucosa,  but  easily  recognized  by  the 
large  vessels  and  the  abundant  connective  tissue.  (c)  The 
muscular  portion  of  the  vaginal  wall. 


202  STUDENTS  HISTOLOGY 


THE    FALLOPIAN    TUBE    OB    OVIDUCT 

The  Fallopian  tube  has  a  serous  coat  derived  from  the  peri- 
toneum; a  muscular  layer,  consisting  of  unstriated  muscular  fibers, 
mostly  disposed  in  a  circular  manner;  and  a  mucous  membrane 
which  lines  the  tube.  The  mucous  membrane  is  covered  with  a 


FIG.  127.    FALLOPIAN  TUBE.    TRANSVERSE  SECTION  OF  A  FOLD  OF  THE 
AMPULLA— AFTER  HENLE. 

*  *  Spaces  between  the  folds. 

single  layer  of  columnar,  ciliated  epithelial  cells,  whose  cilia  create 
a  current  in  the  direction  of  the  uterus.  The  mucous  mem- 
brane has  numerous  longitudinal  folds,  which  are  very  com- 
plicated, and  which,  in  tranverse  section,  appear  like  glands. 
Glands,  however,  are  not  present. 

PRACTICAL     DEMONSTRATION 

Harden  the  Fallopian  tube  of  a  healthy  young  female  in  alcohol  or 
Miiller's  fluid ;  imbed  in  celloidin ;  cut  transverse  sections ;  stain  in  hsernatoxy- 
lin  and  eosin;  mount  in  balsam. 


THE   OVARY  203 

(L.) 

Find  the  three  principal  layers  :  the  mucous  membrane,  with 
its  folds  ;  the  muscular  layer,  consisting  of  unstriated  muscle, 
divided  into  an  inner  circular  and  an  outer  longitudinal  band ; 
and  the  thin  serous  covering. 
(H.) 

The  mucous  membrane  consists  of  a  fibro- elastic  basis,  covered 
by  a  single  layer  of  columnar  ciliated  epithelial  cells,  which  will 
be  found  well  preserved  at  the  bottoms  of  the  folds. 

THE    OVARY 

The  ovary  consists  of  a  stroma  or  ground -substance  of  connec- 
tive and  smooth  muscular  tissue,  in  which  are  scattered  various 
sized  spherical  bodies,  the  Graafian  follicles . 

The  stroma  is  divided  into  three  layers  or  regions,  which  are 
not  very  sharply  differentiated. 

The  free  surface  of  the  ovary  is  covered  with  a  single  layer  of 
low  columnar  epithelial  cells,  called  the  germinal  epithelium. 

Immediately  beneath .  the  epithelium  is  a  thin  layer  of  fibrous 
tissue,  termed  the  tunica  albuginea. 

The  cortex  proper,  or  second  layer,  is  distinguished  by  the 
Graafian  follicles,  which  will  be  described  later. 

The  central  portion  of  the  organ,  the  zona  vasculosa,  is  largely 
occupied  by  thick-walled  blood-vessels,  among  which  the  extremely 
tortuous  arteries  are  especially  evident.  Occasionally  one  may  see 
in  this  region  somewhat  ovoid  nodules  in  varying  degrees  of  retro- 
grade change — the  corpora  lutea.  They  present  the  phenomena 
resulting  from  the  maturation  of  the  follicle  during  menstruation. 
The  accompanying  illustration,  Fig.  128,  was  drawn  from  a  cor- 
pus luteum  which  had  formed  in  the  site  of  a  Graafian  follicle,  the 
contents  of  which  had  escaped  at  some  menstrual  epoch,  and  been 
followed  by  impregnation. 

PRACTICAL    DEMONSTRATION 

The  ovary  of  a  young  animal  is  to  be  preferred.  If  the  organ  cannot  be 
obtained  from  the  human  subject,  the  female  of  almost  any  domestic  animal 
will  provide  an  excellent  demonstration  for  the  histological  elements.  Let  the 
tissue  be  hardened  with  strong  alcohol,  and  sections  be  cuti  vertically  to  the 
free  surface  and  stained  with  hsematoxylin  and  eosin.  The  sections  should 
include  at  least  one-half  the  depth  of  the  organ,  so  as  to  exhibit  all  of  the 
regions. 


204 


STUDENTS    HISTOLOGY 


SECTION     OF     THE     ADULT     HUMAN    OVARY 

OBSERVE  :  (Fig.   1 28) 

(L.) 

1.  The  tunica  albuginea.     (Note  that 'the  layer  is  not  of  uni- 
form thickness,  and  is  composed  largely  of  spindle-shaped  cells,  as 


PIG.  128.     SECTION  OP  AN   OVARY  FROM   A  WOMAN  35  YEARS    OLD.     STAINED  WITH 

H^EMATOXYLIN   AND   EOSIN    (X250). 

A.  Surface  of  the  ovary. 

B.  Stroma. 

C.  Large,  tortuous,  thick-walled  arteries  of  the  central  portion  of  the  organ. 

D.  D.  Small  Graafian  follicles  of  the  superficial  zone. 

E.  Larger  follicles  of  the  deeper  portion. 

F.  Membrana  propria  of  a  Graafian  follicle. 

G.  Membraua  granulosa  of  the  follicle.    The  line  leads  to  the  discus  proligerus. 
H.  An  ovum. 

I.    Germinal  vesicle. 

J.   Germinal  spot. 

K.  An  old  corpus  luteum. 

shown  by  the  numerous  elongated  nuclei.     Search  particularly  for 
and  note  the  character  of  the  epithelial  covering.) 

2.  The  cortical  layer,  containing  numerous  Graafian  follicles, 
and  possibly  a  corpus  luteum.  (Note  the  aggregation  of  the 
smaller  follicles  in  the  extreme  outer  portion  of  the  region.) 


H UMAN   OVARY  205 

3.  The  zona  vasculosa.     (Note  the  unusual  thickness  of  the 
vascular  walls  and  the  irregular  outlines  on  section,  on  account  of 
their  tortuous  course.) 

(H.) 

4.  The  Graafian  follicles.     («•)  Their  diameter,  varying  from 
25  /*•  when   young  to  5  or  10  mm.  when  mature,      (b)   The  mem- 
brana   propria.     (This   is  difficult   to  separate   from    the    stroma 
of  the  ovary  itself,  except  in  more  mature  follicles  than  shown 
in  the  section,      (c)   The  membrana  granulosa.     (This,  in  general, 
appears  to  be  the  outer  layer  of   the  follicle,  on  account  of  the 
difficulty  of  separating   the  membrana   propria  from  the  stroma 
proper  of  the  ovary.     Note  that  it  is  composed,  in  the  smaller  and 
less  mature  follicles,  of  pavement  cells,  and  that  the  cells  become 
thicker  with  maturation,   until  columnar  cells  in  a  single   layer 
result,     (d)  The  ova.     (These  are  contained  within  the  follicles, 
excepting  that  they  may  have  become  detached  during  manipula- 
tion of  the  section,  and  occupy  the  greater  part  of  the  follicles.) 
(e)  The  zona  pellucida  (the   thin  wall  of  the  ovum).     (/)   The 
discus  proligerus.     (This  will  be  recognized  as  a  mass  of  polyhe- 
dral cells,  connecting  the  ovum  at  one  side  with  the  columnar  celts 
of  the   membrana   granulosa.     These   cells   will    proliferate   later 
in   the  development,  and  completely  enclose  the  ovum.)      (g)  The 

.germinal  vesicle.  (Contained  within  the  ovum.  The  contents 
appear  granular ;  it,  as  well  as  the  ovum,  is  fibrillated ;  but  this 
demonstration  cannot  be  made,  excepting  the  animal  be  killed  for 
the  purpose,  and  the  tissue  elements  fixed,  before  changes,  which 
quickly  follow  death,  occur.)  (h)  The  germinal  spot.  (Appear- 
ing as  a  small  dot  within  the  germinal  vesicle.  The  ovum  pre- 
sents the  characteristics  of  what  it  indeed  is — a  typical  cell,  with 
wall,  body,  nucleus,  and  nucleolus.) 

5.  The  corpus  luteum.       (The  example  shown  in  the  drawing 
was  developed  after  the  contents  of  the  Graafian  follicle,  which  it 
represents,  had  suffered  impregnation  ;   and  it  has  arrived  at  the 
later  stage   of   the   series  of   the    phenomena  connected  with    its 
development — the  stage  of  cicatrization.     The  cicatricial  tissue,  to 
which  the  letter  K  points,  indicates  the  remains  of  the  membrana 
granulosa.     Outside  is  seen  the  thickened  membrana  propria,  while 
among  the  contents  will  be  found  pigment -granules  and  fat -glob- 
ules,   imbedded     in     a     structureless,    gelatinous    stroma.       This 
material  results  from  changes  in  the  clot  of  blood  effused  after 
the  escape  of  the  ovum.) 


206  STUDENTS  HISTOLOGY 


FORMATION   OF   THE    OVUM 

As  has  been  previously  shown,  the  ovary  is  covered  with 
columnar  epithelium  ;  and,  singular  as  it  may  appear,  the 
fifty  thousand  Graafian  follicles,  which  it  is  estimated  are  devel- 
oped during  the  life  of  the  human  female,  have  their  origin  in 
these  cells. 

During  foetal  life  this  surface  epithelium  undergoes  a  very 
rapid  proliferation,  and  chains  of  cells  become  imbedded  in  the 
stroma  of  the  ovary.  These  epithelial  prolongations  are  called 
ovarial  or  egg-tubes.  A  little  later  in  the  development,  separate 
portions  or  links  of  these  chains  are  cut  off  by  the  ingrowth  of 
the  stroma.  The  little  groups  of  cells  thus  isolated  become  each 
a  Graafian  follicle. 

Scattered  among  the  columnar  cells,  larger,  more  nearly 
spherical  cells  are  also  found,  the  primordial  ova.  These  are  also 
imbedded  in  the  substance,  and  one  at  least  will  always  be  found 
among  the  minute  collections  of  cells  which  have  been  isolated. 

In  the  process  of  development,  each  group  of  cells  becomes  a 
Graafian  follicle  with  its  contained  ovum,  the  columnar  cells  form- 
ing the  wall  proper,  and  the  primordial  cell  the  ovum,  with  its 
vesicle  and  germinal  spot. 

PRACTICAL     DEMONSTRATION 

The  ovary  from  a  still-born  babe  is  to  be  removed  with  the  scissors, 
exercising  the  utmost  care  that  the  surface  be  not  touched.  The  ovary  of  a 
rabbit  or  guinea-pig  may  also  be  used  with  advantage.  Place  immediately 
in  strong  alcohol,  and  in  twenty-four  hours  it  will  be  fit  for  cutting.  Cut 
extremely  thin  sections  at  a  right  angle  to  the  free  surface  and  including  the 
same;  stain  with  haematoxylin  and  eosin;  mount  in  balsam. 


OVARY    OF    HUMAN    INFANT    (Fig.  129) 

OBSERVE  : 
(L.) 

1.  The  free  surface.     (Note  the  occasional  depressions  which 
mark  the  involution  of  the  epithelial  cells.) 

2.  The   layers.      (Note   the   absence   of   demonstrable   tunica 
albuginea  and  the  great  area  occupied  by  the  cortex.     The  vessels 
of  the  central  portions  are,  unlike  the  ovary  of  mature  life,  large, 
not  numerous,  and  thin-walled.) 


OVARY   OF  HUMAN  INFANT 


207 


(H.) 


3.  The  primordial  ova  of  the  surface  epithelium. 

4.  The  projecting   lines  or  chains  of   epithelium  undivided. 
(Here  the  cells  seem  rather  elongated.) 

5.  Chains  which  are  in  process  of  subdivision. 

6.  Young  Graafian  follicles  in  columns  at  a  right  angle  to 
the  surface  of  the  ovary. 

7.  The  discus  proligerus,  in  many  instances  still  composed  of 
flattened  cells. 

8.  Follicles  showing  discus  proligerus  as  columnar  cells. 

9.  Follicles    showing     great    proliferation    of     discus    pro- 
ligerus. 


FIG.  129.     SECTION  OP  OVARY  OP  CHILD.    DEATH  TEN  DAYS  AFTER  BIRTH  (X350). 

A.  Germinal  epithelium,  covering  surface  of  the  ovary. 

B.  Primitive  ova. 

C.  C.  Projection  of  surface  epithelium  within  the  organ. 

D.  Constriction  of  the  projected  chain  or  cord  of  epithelium  and  isolation  of  portions  to 
form  Graafian  follicles. 

E.  Chain  of  Graafian  follicles.    The  stroma  is  seen  filled  with  previously  formed  follicles 
which  have  now  become  isolated. 

F.  A  large  Graafian  follicle.    It  has  been  cut  in  half  ;    the  ovum  has  fallen  out,  and'  the 
membrana  grunulosa  is  seen  lining  the  cup-shaped  cavity. 

G.  Large  arteries  of  the  central  portion  of  the  ovary. 


208  STUDENTS    HISTOLOGY 

10.  Ova  in  the  early  stages  of  development  from  primordial 
cells,  with  granular  vesicles. 

11.  Instances   of  development  of   two,   possibly  three,   ova 
in  a   single   follicle. 

12.  Large  blood-capillary  supply  of  cortex, — vessels  generally 
parallel  with  the  chains  of  follicles. 

THE   MA  MM  ART    GLAND 

The  mammary  gland  consists  of  acini  lined  by  epithelial  cells. 
The  acini  are  grouped  into  lobules  and  lobes.     There  is  an  abun- 


FIG.  130.    MAMMARY  GLAND  OP  THE  DOG.    TRANVERSE  SECTION  OF  AN  ACINUS 
IN  THE  EARLY  STAGES  OF  FAT  FORMATION.     (HEIDENHAIN.) 

dant  framework  of  fibrous  and  adipose  tissue.  The  ducts  are  lined 
by  columnar  epithelium,  and  open  at  the  nipple.  The  lobules  and 
acini  of  the  resting  gland  are  small.  During  activity  the  acini  are 
lined  by  low  cubical  epithelial  cells  resting  on  a  basement  mem- 


FIG.  131.    MAMMARY  GLAND  OF  THE  DOG  AT  THE  HEIGHT  OF  ACTIVITY. 
(HEIDENHAIN.) 

brane.     Globules  of  oil  form  within  these  cells,  and  are  discharged, 
making  the  oil -globules  of  the  milk. 

The  secretion  of  the  gland  during  the  first  few  days  of  activity 
contains  numerous  cells  in  which  drops  of  oil  are  present,  the 
colostrum-corpuscles.  Sections  of  the  resting  and  active  mam- 
mary gland  of  the  dog  may  be  studied  with  advantage. 


THE  MALE  GENERATIVE  ORGANS 


THE  MALE  GENERATIVE  ORGANS 


THE    TESTICLE 

The  testicle  is  a  glandular  body  (Fig.  132,  T),  oval  in  shape  and 
flattened  laterally.  The  epididymis,  E,  is  an  elongated  and  arched 
structure,  which  is  applied  to  the  upper  end.  and  posterior  border 
of  the  body  of  the  testicle.  It  is  enlarged  at  each  end.  The  upper 
end  is  termed  the  globus  major;  the  lower,  which  is  somewhat 
smaller,  the  globus  minor;  while  between  them  is  the  body  of  the 
epididymis. 

From  the  lower  end  of  the  epididymis  a  hard  convoluted  tube, 


\.  132.  DIAGRAM  OP  THE  COURSE  OP  THE  CANALS  IN  THE  TESTICLE  AND  EPIDIDY- 
MIS, AND  THE  PASSAGE  OF  THE  CANAL  INTO  THE  VAS  DEFERENS.  (LADTH.) 


T.  Testicle. 

Rt.   Rete  testis. 

E    Epididymis. 

PE.  Organ  of  Giraldes. 


Vd.  Vas  deferens. 
*  Vasa  efferentia. 
**  Vas  aberrans. 


the  vas  deferens,  Vd,  is  given  off,  which   soon   straightens,  and 
extends  upward  in  the  spermatic  cord. 

The  testicle  is  almost  completely  covered  with  a  serous  mem- 
brane, the  tunica  vaginalis.  Beneath  that  is  a  strong  fibrous 
capsule,  the  tunica  albuginea,  with  partitions  or  septa  converging 
toward  the  posterior  portion,  the  mediastinum  testis,  or  corpus 


210  STUDENTS  HISTOLOGY 

Highmori.  Between  the  septa  are  delicate  tubular  masses — the 
lobules. 

The  tunica  albuginea  is  the  supporting  framework  of  the  testicle. 
Its  inner  layers  convey  the  blood-vessels,  and  constitute  the  tunica 
vasculosa. 

The  mediastinum  receives  the  blood-vessels  and  contains  also 
the  rete  testis,  Rt,  the  termination  of  the  secreting  tubules. 

Two  or  more  seminiferous  tubules  are  contained  in  each  lobule. 
They  are  fine  thread-like  tubes  closely  packed  together — the  convo- 
luted portion.  As  these  tubules  approach  the  mediastinum  they 


PIG.  133.     TRANSVERSE  SECTION  OF  THREE  SEMINIFEROUS  TUBULES  OF  THE  CAT. 

(SCHAFER.) 

A.  Containing  spermatozoa  least  advanced  in  development. 

B.  More  advanced. 

C.  Containing  fully  developed  spermatozoa. 

join  to  form  a  smaller  number  of  straight  tubes,  or  tubuli  recti. 
The  straight  tubules  enter  the  mediastinum,  making  a  plexus  of 
tubular  spaces,  the  rete  testis,  and  leave  the  rete  testis  at  its  upper 
end  as  fifteen  to  twenty  delicate  ducts,  the  vasa  efferentia,  Fig.  132. 

The  vasa  efferentia,  entering  the  globus  major,  become  coiled 
into  small  conical  masses,  the  coni  vasculosi,  and  open  into  a  single 
convoluted  tube,  the  canal  of  the  epididymis.  This  canal  is  remark- 
ably tortuous;  it  passes  down  the  back  of  the  body  of  the  testicle 
into  the  globus  minor,  and  finally  terminates  in  the  vas  deferens. 

(For  the  character  of  the  lining  epithelial  cells  of  the  different 
parts,  see  page  55. 


THE  MALE  GENERATIVE  ORGANS 


211 


PRACTICAL    DEMONSTRATION 

Harden  the  testicle  of  some  animal,  preferably  a  rat,  in  Flemming's,  Miil- 
ler's,  or  Orth's  fluid.  After  washing,  complete  the  hardening  in  alcohotr 
Imbed  in  celloidin,  cut  transverse  sections,  stain  in  heematoxylin  and  eosin, 
and  mQunt  in  balsam. 

(L.) 

Find  the  tunica  albuginea  covering  the  testicle,  consisting  of 
fibrous  tissue  ;  its  outer  serous  layer;  the  tunica  vaginalis,  and 
its  looser  inner  layers,  containing  many  blood-vessels;  the  tunica 


FIG.  134.    HUMAN  SPERMATOZOA,  HIGHLY  MAGNIFIED.     (RETZIUS.) 

A.  Seen  from  above. 

B.  Head  seen  from  the  side. 

C.  Extremity  of  the  tail. 

vasculosa.  Find  the  thickening  of  the  tunica  albuginea 
behind,  called  the  mediastinum,  from  which  fibrous  septa  arise, 
dividing  the  testicle  into  compartments.  These  compartments  are 
seen  to  contain  seminiferous  tubules  130  p-  to  140  /*  in  diameter, 
cut  at  various  angles. 
(H.) 

Examine  seminiferous  tubules  in  transverse  section.     Observe 
a  lining  of  epithelial  cells  in  several  layers,  and  spermatozoa  in 


212  STUDENTS   HISTOLOGY 

the  central  part  of  the  tube,  in  various  stages  of  formation. 
The  tails  of  the  spermatozoa  point  toward  the  center  of  the 
tube,  and  the  heads  are  directed  toward  the  epithelial  lining. 
Among  the  epithelial  cells  some  may  be  found  that  are  under- 
going karyokinesis. 

Careful  study  of  selected  specimens  has  shown  that  the  epithe- 
lial cells  next  the  basement  membrane  are  of  two  sorts  :  (1)  The 
sustentacular  cells.  (2)  The  spermatogenic  cells.  The  sperma- 
tozoa are  derived  from  the  spermatogenic  cells. 

Spermatozoa  may  be  obtained  from  the  fresh  testicle  or  epidi- 
dymis  of  some  one  of  the  domestic  animals.  The  human  sperma- 
tozoon is  about  50  /*  in  length.  It  consists  of  a  short  oval  head,  a 
short  middle  piece  or  body,  and  a  long  tail.  The  tail  possesses 
active  vibratile  movements. 


THE    P-ROSTATE    GLAND. 

The  prostate  gland  consists  of  a  number  of  tubular  acini,  which 
are  imbedded  in  a  muscular  and  fibrous  framework.  The  muscle 
is  of  the  unstriated  variety,  and  is  very  abundant.  The  tubular 
glands  are  lined  by  columnar  epithelium.  They  open  by  a  num- 
ber of  ducts  into  the  urethra.  Certain  small,  round,  concentrically 
laminated  bodies,  the  prostatic  concretions,  often  occur  in  the  ducts 
and  acini,  especially  in  old  subjects.  The  secretion  of  the  prostate 
gland  is  thin  and  nearly  transparent,  containing  granules  and 
epithelial  cells. 

ERECTILE    TISSUE 

Erectile  tissue  is  best  demonstrated  in  the  penis,  preferably  of  a  human 
infant,  cut  in  transverse  section.  The  two  corpora  cavernosa  and  the  corpus 
spongiosum  are  readily  distinguished.  The  erectile  tissue  can  be  studied  in 
the  corpora  cavernosa. 

The  connective  tissue  surrounding  the  cavernous  bodies  gives 
off  numerous  trabeculse,  forming  a  framework,  enclosing  spaces. 
These  spaces  are  lined  by  endothelium,  and  communicate  with  one 
another  freely.  The  arteries  open  into  them,  and  the  veins  open 
from  them.  During  erection  they  become  greatly  distended  with 
blood.  Similar  erectile  tissue  occurs  in  the  external  generative 
organs  of  the  female. 


THE   SUPRARENAL    BODY  213 


THE   SUPRARENAL    BODY 

This  body  is  attached  by  areolar  tissue  to  the  summit  of 
the  kidney,  and  consists  of  several  folia  or  leaflets.  An  examina- 
tion of  one  of  these  leaflets  will  give  us  an  idea  of  the  organ  as  a 
whole.  The  plan  of  structure  seems  to  be  as  follows: 

In  the  connective  tissue  which  supports  the  folia  are  found 
arterial  branches  derived  from  the  phrenic  and  renal  arteries, 
besides  the  suprarenal  artery  itself.  These  arteries  penetrate  the 
organ,  break  up  immediately  into  capillaries,  which  finally  con- 
verge toward  the  center  of  the  leaflet ;  the  blood  is  here  col- 
lected in  thin -walled  veins,  by  which  it  is  drained  into  the  supra- 
renal vein,  thus  leaving  the  body. 

The  capillary  meshes  vary  in  form  and  size,  according  to  their 
position.  Near  the  circumference  of  the  leaflets  the  meshes  are 
small  and  ovoid;  while,  as  the  center  is  approached,  they  become 
elongated.  These  spaces  between  the  capillaries  are  filled  with 
compressed,  globular,  nucleated  cells,  the  smaller  containing  only 
perhaps  six  or  eight,  while  the  longer  may  be  occupied  by  thirty 
or  forty  of  these  cell -elements,  which  constitute  the  parenchyma 
of  the  organ.  This  variation  in  size  of  the  cell -compartments, 
contributing,  as  it  does,  to  alter  the  appearance  of  the  different 
zones  of  the  tissue,  has  given  rise  to  a  division  into  cortex  and 
medulla.  The  cortex  is  divided  from  without  inward  into  a  zona 
glomerulosa,  zona  fasciculata,  and  zona  reticularis.  Many  nerve- 
fibers  enter  the  organ  with  the  arteries.  They  form  a  plexus, 
mostly  of  non-medullated  fibers,  in  the  medulla.  Ganglion -cells 
are  numerous.  The  surface  is  covered  with  a  fibrous  capsule  con- 
tinuous with  the  supporting  framework. 

The  suprarenal  body  is  also  often  known  as  the  suprarenal 
capsule.  This  body,  the  spleen,  the  thyroid  and  the  thymus 
glands,  with  certain  other  organs  of  less  importance,  are  some- 
times called  "the  ductless  glands  " 

PRACTICAL    DEMONSTRATION 

The  tissue  is  best  hardened  in  strong  alcohol,  and  should  be  cut  as  soon 
as  the  hardening  is  complete.  It  will  be  sufficiently  firm  to  admit  of  the 
thinnest  sections  being  made  free-hand  or  with  a  simple  microtome.  The 
sections,  stained  with  hsematoxylin  and  eosin,  give  excellent  differentiation. 


214 


STUDENTS  HISTOLOGY 


HUMAN    SUPRARENAL    BODY.     (Figs.  135  and  136) 

SECTION  OF  A  SINGLE  LEAFLET,  CUT  TRANSVERSELY  TO  THE 

CENTRAL  VEINS.     STAINED  WITH  H.EMA- 
OBSERVE:  TOXYLIN  AND  EOSIN. 

(L.) 

1.  Section  of  arterial  twigs  on  the  border  of  the  leaflet. 

2.  The  convergence  of  the  parenchyma  toward  the  center. 

3.  The  large  and  thin- walled  central  veins. 

4.  The  small  size  of  the  parenchymatous  areas  on  the  outer 
borders  and  their  elongation  within,  making  the  zona  glomeru- 
losa  and  the  zona  fasciculata  respectively. 

5.  Distinguish  the  zona  reticularis  next  to  the  medulla. 


FIG.  135.    VERTICAL  SECTION  OF  A  SINGLE  LEAFLET  OF  THE  SUPRARENAL 
BODY.     STAINED  WITH  H^EMATOXYLIN  AND  EOSIN  (X  60). 

A.  Fibrous  tissues  surrounding  and  connecting  the  leaflets. 

B.  The  outer  portion,  consisting  of  small  compartments— the  so-called  zona  glomerulosa. 

C.  The  central  elongated  cell-compartments  and  medulla. 

D.  Large,  thin-walled  central  veins. 

E.  Arteries  ramifying  in  the  outer  fibrous  tissue  which  supply  the  parenchyma. 


HUMAN  SUPRARENAL    BODY 


215 


SAME  SECTION  AS  FIG.  135,  MORE  HIGHLY  MAGNIFIED.     ZONA  FASCICU- 
LATA  (X  400). 

A.  Blood-capillaries,  arising  from  the  arteries   seen  in  the  proceeding    illustration,   and 
ramifying  in  the  connective  tissue  framework. 

B.  Compartments— lobules— formed  by  delicate  connective  tissue  prolongations    from  the 
fibrous  capsule. 

C.  Lobular  parenchyma.    These  large,  somewhat  rounded  cells  are  generally  mononucleated, 
contain  fat-globules,  and  are  frequently  pigmented. 

(H.)     Fig.  136. 

1.  The  capillary  plexus,  forming  ovate  or  elongated  meshes. 

2.  The  compressed  globular  cells  of  the  parenchyma.     (Note 
that   the   cells  are  small  in  the  small  compartments,   as  though 
crowded.     This   is   due,  in   a  measure,  to  the   contraction  of   the 
tissue  from  the  rapid  hardening. 

3.  The  minute  fat-globules  in  the  parenchyma. 

4.  Yellow   pigment- granules   in   the   cells,    especially   of    the 
medulla. 


216  STUDENTS    HISTOLOGY 

THE   NERVOUS   SYSTEM 

Structural   Elements 

The  elements  of  the  nervous  system  are  : 

1.  Nerve -Fibers. 

2.  Nerve -Cells. 

3.  Connective   Tissue  and  Neuroglia. 

4.  Peripheral  Termini. 

NERVE-FIBERS 

Nerve -fibers  are  of  two  sorts,  medullated  or  white,  and  non- 
medullated  or  gray. 

A  typical  medullated  nerve-fiber  consists  of  three  portions;  viz., 
a  central  conducting  portion,  the  axis -cylinder;  the  medullary 
sheath,  or  white  substance  of  Schwann;  and  the  enveloping  connec- 
tive tissue  substance,  the  neurilemma.  Such  fibers  are  found 
largely  in  the  trunks  of  the  cerebro- spinal  system,  while  medul- 
lated fibers  devoid  of  the  neurilemma  exist  in  the  optic  and 
acoustic  nerves,  the  spinal  cord,  and  the  brain. 

The  axis -cylinder  may  be  seen  to  be  split  up  longitudinally, 
and  is  found  to  be  composed  of  fine  primitive  or  ultimate  fibrillae, 
which  may  present  minute  varicosities  or  swellings  at  irregular 
intervals. 

The  white  substance  of  Schwann,  which  is  largely  fatty,  pre- 
sents under  the  microscope  the  most  prominent  feature  of  medul- 
lated nerves,  affording  a  nearly  complete  investment  of  the  nerve- 
axis. 

The  neurilemma  is  an  elastic  envelope,  which  completely 
invests  the  medullary  substance.  This  tubular  membrane  is 
nucleated,  and  at  intervals  is  constricted  so  as  to  reach  the  axis- 
cylinder.  These  constrictions  are  called  the  nodes  of  Ranvier. 
The  neurilemma  presents  a  single  nucleus,  with  a  small  amount  of 
protoplasm  between  each  two  of  these  nodal  points.  The  con- 
strictions do  not,  however,  affect  the  even  caliber  or  continuity 
of  the  axis -cylinder. 

The  distance  between  two  nodes  of  Ranvier  may  be  as  much  as 
a  millimeter,  or  it  may  be  less  than  that. 

Non-  medullated  nerve -fibers   are   found   chiefly  in  the  sympa- 


THE   NERVE-TRUNKS  217 

thetic  system.  But  some  non-medullated  fibers  occur  in  most  of 
the  cerebro- spinal  nerves,  and  they  form  the  chief  part  of  the 
olfactory  nerve.  Non-medullated  nerve -fibers  have  an  axis -cylin- 
der and  a  neurilemma,  but  no  medullary  sheath.  They  branch 
freely,  and  aid  in  the  formation  of  plexuses.  There  are  numerous 


FIG.  137.     SEPARATED  NERVE-FIBERS  (X  400). 

A.  Neurilemma  of  a  fiber. 

B.  White  substance  of  Schwann,  stained  with  osmic  acid,  which  hides  the  axis-cylinder. 

C.  Nucleus  of  the  neurilemma. 

D.  One  of  Ranvier's   nodes  in  an  osmic  acid  -  stained   fiber,   showing    the   axis-cylinder 

between  the  separated  portions  of  Schwann's  sheath. 

E.  A  medullated    fiber,  teased    in  normal  salt  solution.    The   medullary   substance  has 

become  coagulated  on  exposure  and  removal.    The  axis-cylinder  is  faintly  seen. 

F.  Axis-cylinder  at  torn  extremity. 
CT.  Non-medullated  fiber. 

nuclei  beneath  the  neurilemma.  The  neurilemma  is  wanting  in 
some  situations.  The  medullated  nerve -fibers  also  lose  the  medul- 
lary sheath  when  they  are  about  to  enter  upon  their  peripheral 
distribution. 

THE    NERVE-TRUNKS 

The  structure  of  nerve -trunks  is  most  typical  in  the  large 
nerves  composed  of  medullated  nerve -fibers.  In  transverse  sec- 
tions, medullated  nerve -fibers  appear  like  small  round  cells,  in 
which  the  axis -cylinders  resemble  nuclei.  The  nerve -fibers  are 
collected  into  bundles  called  funiculi. 

The  connective  tissue,  which  serves  to  unite  the  elements  of  a 
nerve -trunk,  does  not  differ  materially  from  the  sustentacular  tis- 
sue of  other  organs.  Different  terms  are  applied,  according  to  its 
use  and  location,  as  follows  : 


218 


STUDENTS   HISTOLOGY 


EPINEURIUM. — Forming  the  sheath  of  the  entire  nerve -trunk. 

PERINEURIUM. — Surrounding  the  funiculi  composing  the  nerve- 
trunk. 

ENDONEURIUM. — Surrounding  and  uniting  the  nerve-fibers  of  the 
funiculi. 

NEURILEMMA. — Surrounding  the  individual  nerve -fibers  of  a 
bundle. 


FIG.  138.     TRANSVERSE  SECTION  OF  THE  ANTERIOR  CRURAL  NERVE  (X  250). 

A.  The  epineurium. 

B.  Adipose  tissue  in  the  loose  areolar  tissue  of  the  sheath. 

C.  Lymph-spaces  of  the  epineurium. 

D.  Large  blood- vessels  of  epineurial  sheath. 

E.  Perineurium  surrounding  funiculi. 

F.  Lymph-spaces  of  last. 

G.  Medullated  nerve-fibers  in  T.  S.  supported  by  connective  tissue  — endotieurium. 


The  formula  E.  P.  E.  N.,  composed  of  the  initials  of  the  nances 
of  the  investments  from  without  inward,  will  aid  the  memory. 

The  epineurium  serves  to  protect  the  nerve  in  its  course,  and 
to  support  the  nutrient  blood-vessels  and  the  channels  of  lym- 
phatics. The  fibers  run  both  longitudinally  and  transversely. 
The  perineurium,  arranged  in  dense  bands,  forms  distinct  sheaths 


NERVE-CELLS  219 

for  the  funiculi,  the  fibers  running,  for  the  most  part,  circularly. 
The  endoneurium  not  infrequently  divides  the  nerve -bundles  into 
smaller  or  primitive  bundles.  It  supports  the  blood -capillaries, 
contains  small  lymph -spaces,  and  its  nuclei  are  frequently  large 
and  prominent.  The  larger  nerve -trunks  have  their  own  nerves 
distributed  to  the  epineurium,  —  nervi  nervorum. 

The  final  distribution  of  the  elements  of  a  nerve -trunk  is 
effected  by  subdivision,  first,  of  the  large,  and  afterward  of  the 
primitive  bundles  or  funiculi.  The  perineurial  sheaths  are  pro- 
longed, surrounding  the  dividing  bundles,  even  to  their  final  distri- 
bution, where,  around  terminal  and  single  medullated  fibers,  the 
sheath  remains  as  a  layer  of  exceedingly  delicate  flattened  cells. 
The  necessity  for  the  endoneurium  ceases  with  the  ultimate  sub- 
division of  the  funiculus. 

.  The  medullated  nerve -fibers,  when  they  reach  the  point  of 
their  final  distribution,  branch  at  a  node  of  Ranvier,  and  also  lose 
the  medullary  sheath. 

PRACTICAL    DEMONSTRATION 

Medullated  nerve-fibers  can  be  studied  best  in  preparations  that  have 
been  teased  on  a  slide.  It  requires  much  care  and  patience  to  separate  tho 
single  nerve-fibers  of  a  bundle.  The  student  should  use  nerve-tissue  that 
was  fixed  with  osmic  acid  while  fresh  (see  page  23).  The  medullary  sheaths 
are  black.  Also,  tease  nerve-fibers  that  were  hardened  in  Muller's  fluid  and 
afterwards  washed  and  transferred  to  alcohol.  Stain  the  fibers  on  the  slide 
with  Van  Gieson's  picric  acid  and  acid  fuchsin  mixture  (page  32),  omitting 
the  heematoxylin.  Dehydrate  with  a  few  drops  of  alcohol  in  succession, 
which  may  be  removed  with  blotting-paper  ;  clear  with  a  drop  of  oil  of 
cloves  ;  mount  in  balsam.  The  axis-cylinders  and  nuclei  are  red  ;  the  med- 
ullary sheaths  are  yellow  ;  the  nodes  of  Ranvier  are  distinctly  visible. 

A  nerve  that  has  been  hardened  in  Miiller's  fluid  should  be  imbedded 
in  celloidin,  and  transverse  sections  cut ;  stain  with  ha3matoxylin  and  Van 
Gieson's  picric  acid  and  acid  fuchsin. 

NERVE-CELLS 

The  cells  of  the  nerve -centers  are  usually  called  ganglion -cells. 
They  differ  greatly  in  size,  some  of  the  largest  measuring  100  p*  or 
more  in  diameter.  The  nucleus  is  round,  conspicuous,  and  has  a 
nucleolus.  The  protoplasm  sometimes  contains  pigment.  The 
cells  are  surrounded  by  minute  lymph -spaces.  Ganglion -cells 
exhibit  various  shapes,  some  being  spherical,  others  pyriform  or 
stellate.  The  differences  in  outline  are  due,  in  part,  to  the  pro- 


220 


STUDENTS   HISTOLOGY 


cesses,  of  which  there  may  be  one  or  many.  According  to  the 
number  of  processes,  the  cells  are  sometimes  named  unipolar, 
bipolar,  or  multipolar.  Every  ganglion-cell  has  a  relatively  straight 
process,  which  is  the  axis -cylinder  process.  The  other  processes, 
when  they  are  present,  divide  and  subdivide  rapidly,  to  form  fine 
networks  or  arborizations.  They  are  called  protoplasmic  processes, 


FIG.  139.     TYPES  OF  GANGLION-CELLS  AS  SHOWN  BY  GOLGI'S  METHOD.     (BAKER.) 

A.  Type  I.  *    Axis-cylinder  process  with  collaterals. 

B.  Type  II.  *  Axis-cylinder  process. 

or  dendrites.  The  development  of  protoplasmic  processes  is  seen  in 
an  extreme  degree  on  the  ganglion -cells  of  Purkinje  in  the  cere- 
bellum (Fig.  158).  It  is  probable  that  the  processes  of  one  cell  do 
not  unite  with  those  of  any  other,  and  that  whatever  physiologi- 
cal relations  the  cell  has  with  other  cells  are  established  through 
proximity,  but  not  by  continuity  of  substance.  The  researches 
made  according  to  Golgi's  method  of  impregnating  tissues  with 
silver  have  shown  that  ganglion-cells  are  of  two  principal  types  : 


NERVE-CELLS 


221 


FIG.  140.    DIAGRAM  OP  THE  LOWER  MOTOR  NEURONE.     (BARKER.) 


D.  A  motor-cell  from  the  anterior  horn  of  the  spinal  cord,  with  its  protoplasmic 

processes. 

Ax.  Axis  cylinder  process.  N.  of  N.  Nucleus  of  neurilemma. 

S.  F.   Collaterals.  Tel.  The  ending,  in  striped  muscle-fiber,  M'. 

M.  Medullary  sheath.  N.  The    nucleus,   and    N'    nucleolus   of    the 

N.  R.  Node  of  Ranvier.  ganglion-cell. 


222  STUDENTS  HISTOLOGY 

TYPE  I.  The  cell  has,  besides  the  protoplasmic  processes,  an 
axis  -  cylinder  process  which  becomes  continuous  with  the  axis- 
cylinder  of  a  nerve -fiber  usually  having  a  considerable  length. 
Minute  offshoots  are  given  from  the  axis  -  cylinder  process,  which 
are  called  collaterals  (Fig.  139,  A). 

TYPE  II.  In  this  case  the  axis -cylinder  process  divides  repeat- 
edly and  soon  after  leaving  the  ganglion -cell,  forming  a  network 
within  the  nerve -center  (Fig.  139,  B). 

A  ganglion -cell  with  its  axis -cylinder  process  is  called  by  many 
writers  a  neurone.  In  the  case  of  some  of  the  medullated  nerve- 
fibers  proceeding  from  the  cerebro  -  spinal  centers,  the  terminal 
distribution  of  the  axis -cylinder  may  be  as  much  as  a  meter 
distant  from  the  ganglion -cell  (Fig.  140). 

NEUROGLIA 

The  brain  and  spinal  cord  have  a  supporting  framework  of 
ordinary  connective  tissue  which  enters  at  the  surface  from  the 
pia  mater.  They  possess,  besides,  a  special  form  of  supporting  tis- 


FIG.  141.     NEUROGLIA  FROM  BENEATH  THE  PIA  MATER  OF  THE  SPINAL  CORD. 

(X  400.) 

A.  Network  of  neuroglia-fibrils. 

B.  Spider  (Belter's)  cells. 

C.  Nerve-fibers  in  T.  S. 

sue  called  neuroglia.  It  ctmsists  of  a  fine  reticulum  produced  by  the 
interlacing  of  large  numbers  of  delicate  processes,  which  arise  from 
neuroglia  cells.  These  cells  have  a  stellate  outline,  and,  with  their 


TEE   PERIPHERAL    NERVE-ENDINGS 


223 


numerous  processes,  suggest  a  spider  and  its  legs  (Figs.  139  and 
155).  Some  forms  are  described  as  "moss -like."  Neuroglia- cells 
are  well  shown  in  silver -stained  specimens.  The  neuroglia  of  the 
spinal  cord  is  intimately  related  with  the  epithelium  lining  the 
central  canal,  from  which  it  originated.  Neuroglia,  unlike  the 
other  supporting  tissues,  is  derived  from  the  ectoderm. 


THE    PERIPHERAL    NERVE-ENDINGS 

The  terminal  branches  of  the  nerves  are  so  complex  in  struc- 
ure  and  so  difficult  of  demonstration  that  only  a  few  of  the  most 
important  can  be  considered  in  this  work. 

Sensory  nerves  sometimes  present  free  endings,  as  in  the  strati- 
fied epithelium  of  the  epidermis  and  cornea.  The  medullated  nerve- 
fiber  loses  its  medullary  sheath  at  a  node  of  Ranvier,  and  divides 
repeatedly,  making  a  plexus  of  minute  fibrillae  in  the  connective 
tissue,  or  just  below  the  epithelium,  or  between  the  epithelial  cells. 

Special  sensory  endings  are  more  complex  in  structure. 
Examples  are  found  in  the  tactile  corpuscles,  which  occur  in  the 
papillae  of  the  skin.  They  are  oval  bodies  having  numerous  nuclei. 


TERMINATION  OP  NERVE -FILAMENTS  IN  THE  EPITHELIUM  OF  THE  CORNEA. 
(RANVIER.) 

One  or  more  medullated  nerve -fibers  enter  at  the  base,  losing  their 
medullary  sheaths.  The  axis -cylinders  break  up  into  fibrils,  which 
here  and  there  present  expansions. 

The  Pacinian  bodies  or  corpuscles  of  Vater  are  easily  found 
in  the  mesentery  of  the  cat,  where  they  are  numerous  and  visible 
to  the  unaided  eye.  They  are  oval  in  form  and  nearly  transparent. 
The  most  prominent  part  is  the  capsule,  which  consists  of  lamellas 
of  connective  tissue,  which  are  concentric,  and  resemble  the  layers 


224 


STUDENTS    HISTOLOGY 


FIG.  143.     TACTILE   CORPUSCLE   FROM  THE   SKIN   OF  THE   PALMAR  SURFACE  OF   THE 
INDEX  FINGER  OF  MAN.     (RANVIER.) 

a.  Terminal  nerve-fibrils, 
n.  Afferent  nerve. 


Fia.   144.     PACINIAN    CORPUSCLE  FROM    THE  MESENTERY  OF  THE  CAT.     (RANVIER.) 

c.    Capsule. 

m.  Inner  bulb. 

f,  n.  Afferent  nerve. 


NERVE-ENDINGS  IN  MUSCLE 


225 


of  an  onion.  A  medullated  nerve -fiber  enters  at  the  bottom,  and 
soon  loses  its  medullary  sheath.  The  free  axis -cylinder  terminates 
in  a  rounded  or  bulb -like  extremity,  surrounded  by  a  homogenous 
substance,  the  inner  bulb. 

The   special   form    of    nerve -endings,   called   taste-buds,   have 
already  been  described   (page  149). 


NERVE -ENDINGS    IN    MUSCLE 


The  plexuses  of  non  -  medullated  nerves  supplying  non- striated 
muscle  have  often  been  referred  to  (pages  154  and  160).  From 
these  plexuses  minute  fibrillae  extend  among  the  muscle -cells. 
Their  exact  mode  of  termination  has  not  been  definitely  determined. 


FIG.   145.    NERVE-ENDING  IN  STRIATED  MUSCLE-AFTER  KUHNE. 

The  medullated  nerves  supplying  striated  muscle  form  an  intra- 
muscular plexus.  Bundles  of  nerve -fibers  start  from  this  plexus, 
one  nerve -fiber  going  to  each  muscle -fiber.  The  medullary  sheath 
is  lost.  The  axis -cylinder  breaks  up  into  twisted  fibrillae,  with 
bulbous  ends.  These  constitute  the  end -plate,  which  probably  lies 
below  the  sarcolemma,  and  is  imbedded  in  nucleated  protoplasm, 
the  sole -plate. 


226 


STUDENTS   HISTOLOGY 


SPINAL   CORD 

The  membranes  covering  the  spinal  cord  will  be  discussed 
later;  see  page  235. 

The  spinal  cord  is  composed  of  gray  matter  (cellular)  and 
white  matter  (consisting  of  nerve-fibers),  and  serves  as  a  medium 
of  communication  between  the  brain  and  the  peripheral  nerve- 
apparatus.  The  arrangement  of  its  several  parts  will  be  best 
understood  by  the  study  of  a  transverse  section,  of  which  Fig. 
146  is  a  diagrammatic  representation. 

The  gray  substance  occupies  the  central  portions  of  the  struc- 


FIG.  146.    DIAGRAM.    CERVICAL  SPINAL  CORD  IN  TRANSVERSE  SECTION. 

A.  Anterior  median  fissure. 

B.  Posterior  median  fissure. 

C.  Anterior  or  ventral  horn. 

D.  Posterior  or  dorsal  horn. 

E.  Point  of  emergence  of  anterior  root  of  spinal  nerve. 

F.  Posterior  root  of  spinal  nerve. 

G.  White  commissure. 

H.  Anterior  gray  commissure. 
I.  Posterior  gray  commissure. 
J.  Substantia  gelatinosa  Rolandi. 

The  tracts  which  are  named  on  the  diagram  have  no  definite  boundaries    histologically. 
They  are  physiological  areas. 


SPINAL    COED  227 

ture,  and  consists  of  two  lateral  masses  and  a  connecting  link,  or 
commissure.  Near  the  central  portion  of  the  figure,  a  small  cir- 
cular opening  occurs — the  transversely  divided  central  canal. 


FIG.  147.    HUMAN  SPINAL  CORD  FROM  THE  DORSAL  REGION,  STAINED  BY  THE 
WEIGERT-PAL  METHOD.     SLIGHTLY  MAGNIFIED.    PHOTOMICROGRAPH. 

is  in  communication,  in  the  medulla,  with  the  fourth  ventri- 
cle, and  will  serve  as  a  starting  point  for  our  study. 

The  gray  matter  completely  surrounds  the  central  canal,  and 
its  outline  resembles  the  capital  H,  or  a  pair  of  crescents  with 
their  concavities  looking  outwards.  The  anterior  (or  ventral) 
horns  or  cornua  are  blunt.  The  posterior  (or  dorsal)  horns  are 
pointed.  There  are  lateral  projections  from  the  anterior  horns, 
sometimes  called  lateral  horns.  They  lie  opposite  the  central 
canal,  and  are  most  marked  in  the  upper  thoracic  region.  The 
crescents  are  connected,  a  portion  of  the  connecting  substance 
passing  in  front  and  a  portion  behind  the  central  canal — the 
anterior  and  posterior  gray  commissural  bands.  The  amount  of 
gray  matter  is  greatest  in  the  cervical  and  lumbar  enlargements 
of  the  cord  (Fig.  148). 

The  white  substance  is  divided  anteriorly  by  the  anterior 
median  fissure,  which  cuts  into  the  cord  nearly  to,  but  not  quite 
as  far  as  the  anterior  gray  commissure.  A  corresponding  division 
appears  posteriorly  (the  posterior  median  fissure),  which  does  not 
divide  the  cord  posteriorly,  but  the  division  is  indicated  by  a  band 
of  pia  mater,  which  penetrates  entirely  to  the  posterior  gray  com- 
missure. The  two  masses  of  white  substance  thus  indicated  are 
roughly  divided  into  anterior,  lateral,  and  posterior  columns  by 


228  STUDENTS   HISTOLOGY 

the  horns  of  gray  matter.  They  are  united  just  in  front  of  the 
anterior  gray  commissure  by  white  matter — the  white  commissure. 
The  spinal  nerves  take  origin  from  the  gray  cornua,  the  anterior 
roots  from  the  anterior,  and  the  posterior  roots  from  the  posterior 
cornua.  The  white  substance  consists  essentially  of  medullated 
nerve -fibers  which,  with  the  exception  of  the  anterior  spinal 
nerve -roots  and  the  commissural  fibers,  pass  mainly  in  a  longi- 
tudinal direction. 

The  anterior,/ lateral,  and  posterior  columns    into  which   the 
white   matter   isi  primarily   divided,  may   be   divided   secondarily 


FIG.  148.    HUMAN  SPINAL  CORD  FROM  THE  LUMBAR  REGION.     STAINED  BY  THE 
WEIGERT-PAL  METHOD.    SLIGHTLY  MAGNIFIED.    PHOTOMICROGRAPH. 

into  certain  other  columns  or  tracts  which  are  indicated  in  Fig, 
146.  These  tracts  are  often  called  by  the  name  of  the  discoverer. 
The  principal  ones  are  as  follows  : 

The  direct  pyramidal  tract:  Tiirck. 

The  ascending  antero -lateral  tract:  Gowers. 

The  descending  antero -lateral  tract. 

The  crossed  pyramidal  tract. 

The  direct  cerebellar  tract. 

The  postero- external  tract — funiculus  cuneatus:  Burdach. 

The  postero -internal  tract— funiculus  gracilis:  Goll. 

The  demonstration  of  the  different  tracts  we  owe  partly  to 
pathology,  since  in  certain  diseases'  definite  tracts  may  be  involved 
throughout  the  length  of  the  cord,  while  the  others  may  be  exempt. 
The  alterations  which  ensue  in  the  diseased  parts  make  it  easy  to 
trace  such  tracts. 


SPINAL    COED  229 

Embryological  study  has  shown  also  that  the  medullary  sheath 
appears  at  different  periods  of  development  in  the  different  tracts 
of  nerve-fibers,  although  the  time  is  constant  for  each  particular 
tract.  The  presence  of  the  sheath  in  certain  tracts,  and  its  absence 
in  others,  makes  it  possible  to  outline  the  tracts  in  a  series  of 
embryonic  cords. 

Physiological  experiments  demonstrate  the  functions  belonging 
to  certain  tracts. 

PRACTICAL    DEMONSTRATION 

Nerve-tissue  should,  under  all  circumstances,  be  hardened  in  Miiller's 
fluid.  The  cord  should  be  obtained  as  nearly  fresh  and  uninjured  as  possi- 
ble, cut  transversely  with  a  sharp  razoj1  into  pieces  a  centimeter  long,  and 
placed  immediately  in  the  fluid— in  the  proportion  of  a  liter  of  the  mixture 
to  100  grams  of  tissue.  The  solution  should  be  thrown  away  after  twenty- 
four  hours,  and  a  fresh  supply  provided.  It  should  be  again  changed  after 
three  days,  and  again  after  another  week.  After  four  weeks  the  bichromate 
should  be  poured  off,  and  the  tissue  rinsed  once  with  water,  after  which 
the  hardening  is  to  be  completed  with  alcohol  in  the  ordinary  manner. 

After  hardening,  pieces  from  the  different  regions  should  be  cut,  and 
this  is  best  effected  after  imbedding.  Transverse  sections  are  the  most[  instruc- 
tive, although  the  student  should  afterward  study  longitudinal  sectiobs.  The 
sections  may  be  stained  with  hsematoxylin  and  eosin.  Sections  should  also 
be  stained  by  the  Weigert-Pal  method.  For  this  purpose  the  hardening 
must  be  done  with  great  care,  and  must  be  continued  longer.  The  pieces  of 
tissue  are  placed  in  alcohol  direct  from  Miiller's  fluid  without  washing.  The 
details  of  the  method  are  given  on  page  30.  The  Golgi  method  presents  too 
many  difficulties  to  be  attempted  by  any  but  advanced  students. 


HUMAN    SPINAL    CORD — CERVICAL    REGION — TRANSVERSE 
SECTION     (Fig.  149) 

OBSERVE  : 
(L.) 

1.  General  arrangement  of  gray  and  white  substance,  with 
the  latter  surrounding  the  former,  which  resembles  in  outline  the 
letter  H. 

2.  Subdivisions  of   white  substance.      (a)  Anterior  median 
fissure.     (Note  its  passage  inward  and  its  cessation  before  reach- 
ing the  gray  substance.)      (b)   Posterior  median  fissure.     (Note 
its  shallowness  as  a  true  fissure,  and  the  extension  of  the  connec- 
tive tissue  from  the  bottom  inward,   until   the  gray  substance  is 
met.     Compare  the  two  median  fissures.)      (c)  The  emergence  of 
the  anterior  nerve-roots.      (This  provides  the  external  or  lateral 


230 


STUDENTS   HISTOLOGY 


boundary  of  the  anterior  white  columns,  the  internal  boundaries 
being  provided  by  the  anterior  median  fissure.)  (d)  The  lateral 
columns.  (These  contain  the  fibers  of  the  crossed  pyramidal  tract, 
and  include  the  white  substance  between  the  anterior  nerve -roots 
and  the  posterior  gray  cornua.  Each  lateral  column  contains 
nerve-fibers  which  pass  to  the  cerebellum — direct  cerebellar  tract ; 
observe  that  these  tracts  have  no  internal  histological  boundary. 
Note  the  numerous  prolongations  of  the  pia  mater  inward  in  the 
lateral  columns  and  blood-vessels  in  them,  (e)  The  postero-in- 


PIG.  149.     TRANSVERSE  SECTION  OP  THE  SPINAL,  CORD.    MIDDLE   CERVICAL 

REGION  (X  60). 

A.  Anterior.  B.  Posterior. 

This  section  was  made  from  the  cord  of  a  man  who  died  at  the  age  of  75  years,  from 
senile  dementia.    The  gray  substance  appeared  normal,  but  of  somewhat  diminished  area. 

ternal  or  column  of  Goll—funiculus  gracilis.  (These  columns 
occur  on  either  side  of  the  posterior  median  fissure,  and  are 
bounded  laterally  by  a  prolongation  from  the  pia  mater.)  (/) 
The  postero-external  column — funiculus  cuneatus.  (Bounded 
internally  by  the  postero- internal  column,  and  externally  by  the 
posterior  gray  cornu.)  (0r)  The  white  commissure.  (Note  the 


SPINAL    CORD 


231 


absence  of  a  white  commissure  posteriorly,  the  posterior  median 
septum  reaching  the  gray  substance.) 

3.  Subdivisions    of    the   gray   substance,     (a)    The    central 
canal.     (Its  size  and  shape  vary  a  good  deal  at  different  levels.) 
(b)   The  gray  commissures,  anterior  and  posterior,     (c)   The  gray 
columns,     (d)  The  anterior  gray  cornua,  broad  and  not  reaching 
the  periphery  of   the  cord  section,     (e)    The   posterior   cornua, 
narrow  and  passing  completely  out,  posteriorly,   to  form  the  pos- 
terior root  of  a  spinal  nerve. 

(H.) 

4.  The  white  substance.  (Select  a  field,  e.  g.,  in  the  anterior 


PIG.  150.     SAME  SPECIMEN  AS  SHOWN  IN  FIG.  149.    MORE  HIGHLY  MAGNIFIED. 
REGION  OF  ANTERIOR  CORNU  (X  350). 

A.  Medullated  filaments  passing  out  from  the  gray  substance  to  form  the  anterior  root 
of  a  spinal  nerve. 

B.  Ganglion-cells. 

C.  Neuroglia-nuclei. 
I).   Blood-vessels. 

E.  One  of  the  transversely  divided  medullated  fibers  of  the  white  substance,  anterior  to 
the  anterior  gray  cornu.    The  line  leads  to  the  neurilemma. 

F.  White  substance  of  Schwann— of  E. 

G.  The  axis-cylinder  of  E. 

median  column,  and  observe  the  transversely  divided  nerves.) 
(a)  The  nerves  are  not  collected  into  funiculi,  but  each  fiber 
pursues  an  independent  course,  (b)  The  axis-cylinders,  which 
suggest  cell-nuclei.  (Note  the  great  variation  in  size.)  (c)  Most 
of  the  axis -cylinders  surrounded  by  more  or  less  concentric  rings 


232  STUDENTS   HISTOLOGY 

of  translucent,  unstained  white  substance  of  Schwann.  (These 
are  medullated  fibers.  In  the  spinal  cord  a  neurilemma  is  wanting 
for  these  fibers.  With  the  Weigert-Pal  method  the  medullary 
sheaths  are  stained  black  and  their  course  is  easily  traced.) 

(d)  The  small  deeply  haematoxylin- stained  cells  of  the  neuroglia. 

(e)  The  neuroglia-substance,   finely  granular  or    fibrillated,   be- 
tween the  nerve -fibers.      (/)    The  spider  cells   (Deiter's)    of   the 
neuroglia.      (These  are  not  numerous,  but  easily  found  near  the 
periphery.)      (g)   The  longitudinal  nerve-fibers  passing  from  the 
anterior  gray  corau  to  form  the  anterior  root  of  a  spinal  nerve. 
(h)   The  different  size  of  the  nerve-fibers  in  different  areas  of 
the  section.     Note  the  small  fibers  of  the  postero- internal  column. 
With  certain  exceptions,  the  larger  fibers  belong  to  motor  tracts 
and  the  smaller  fibers  to  sensory  tracts,     (i)  The  blood-vessels. 
(These  vessels  are  largely  confined   to  the  fibrous  septa,    which 
pass  in  from  the  pia.) 

5.  The  gray  substance,  (a)  The  central  canal.  (The  canal 
is  lined  with  columnar  ciliated  cells  in  a  single  layer.  The  cilia  are 
rarely  demonstrable  in  the  human  cord,  except  in  children.  The 
central  canal  in  adults  is  often  partly  occluded.  Observe  the  clear, 
homogeneous  ground-substance, —  substantia  gelatinpsa  centralis. 
Compare  it  with  a  similar  mass  covering  the  posterior  horn, —  the 
substantia  gelatinosa  Rolandi.)  (&)  The  ground  -  substance. 
(This  consists,  first,  of  exceedingly  minute  fibers,  formed  by  the 
repeated  subdivision  of  the  axis-cylinders — the  primitive  fibrillae ; 
second,  of  the  delicate  neuroglia-fibers.  It  is  usually  difficult 
in  a  section  to  differentiate  between  the  two.  The  details  can  only 
be  made  out  in  preparations  stained  with  silver  by  Golgi's  method.) 
(c)  Large  ganglion-cells.  (In  the  anterior  horn.  The  straight, 
unbranching  axis -.cylinder  process  can  frequently  be  distinguished. 
Note  the  large,  shining  nucleus  and  the  deeply  stained  nucleolus. 
These  cells  are  frequently  deeply  pigmented.  They  may  be  divided 
into  two  or  three  separate  groups.)  (d)  Small  ganglion-cells. 
(Best  seen  in  the  posterior  horn.  In  the  dorsal  cord  a  collection  of 
medium  sized  cells  appears  at  the  point  where  the  gray  commis- 
sure joins  the  posterior  horn, —  the  column  of  Lockhart  Clarke.) 
(e)  The  lateral  horn  also  contains  small  ganglion -cells.  Occa- 
sional outlying  ganglion -cells  appear  in  the  white  matter  of  the 
antero-lateral  and  posterior  columns.  (/)  Pericellular  lymph- 
spaces.  '(Observed  as  a  somewhat  clear  space  around  the  ganglion- 
cells.)  (g)  Blood-vessels.  (These  are  much  more  numerous  here 


SPINAL    CORD 


233 


than  in  the  white  portion  ;  and  arteries  of  considerable  size  may 
frequently  be  found.)  (h)  Peri-vascular  lymphatics.  (Find  an 
artery  in  transverse  section,  and  observe  the  clear  space  around  it, 
which  may  be  mistaken  for  the  result  of  contraction  of  the  tissue 
in  hardening.  Careful  study  will  reveal  minute  branches  of  cells, 
passing  between  the  adventitia  of  the  blood-vessel  and  the  wall  of 
the  lymph -space.) 

The  course  of  the  axis-cylinders  in  the  cord,  and  their  relations 
with  the  ganglion-cells  of  the  gray  matter,  are  extremely  intricate. 
The  Gelgi  method,  in  the  hands  of  Ramon  y  Cajal  and  others, 
has  been  the  means  of  clearing  up  many  of  the  obscure  parts  of 
this  subject.  The  limits  of  the  present  work  will  only  permit  of 


FIG.  151. 


LARGE  GANGLION-CELLS  OF  THE  ANTERIOR  HORN  OF  THE  SPINAL  CORD. 
Low  POWER.    PHOTOMICROGRAPH. 


allusion  to  a  few  of  the  most  important  facts.  In  this  connection, 
it  is  well  to  recall  the  description  and  diagram  of  a  neurone  (page 
222).  The  central  nervous  system  is  supposed  to  consist  of  many 
neurones.  According  to  this  theory,  several  neurones  may  operate 
together,  one  superimposed  on  another.  It  is  to  be  remembered 
that  the  processes  of  ganglion -cells  probably  do  not  anastomose 
with  those  of  other  ganglion -cells. 

The  large  ganglion-cells  of  the  anterior  horns  of  gray  matter 
give  off  axis -cylinder  processes  to  the  anterior  motor  nerve-roots. 
Some  ganglion -cells  (column  cells)  have  axis -cylinder  processes 
which  run  vertically  in  the  white  matter  of  the  anterior  and  lateral 


234 


STUDENTS   HISTOLOGY 


FIG.  152.  DIAGRAM  OF  THE  RELATIONS  OF  THE  CELLS  AND  FIBERS  OF  THE  SPINAL 
CORD.  (BAKER,  AFTER  LENHOSSEK.) 

The  right  side  shows  the  cells  of  different  classes  found  in  the  cord,  and  their  processes.  The 
left  side  gives  the  processes  of  cells  whose  bodies  are  either  beyond  the  cord  or  at  other  levels, 
with  the  distribution  of  their  collaterals. 

a,  a.  Motor  cells  of  the  anterior  horn. 

c.  Commisstiral  cells. 

d.  Golgi  commissural  cell. 

e.  e.  Columnar  cells  of  antero-lateral  column. 

f.  f.    Columnar  cells  of  posterior  column. 

g.  Golgi  cell  of  posterior  horn. 

1.  Fibers  of  posterior  root  forming  the  antero-posterior  reflex  tract. 

2.  Fibers  passing  to  the  column  of  Clarke. 

3.  Commissural  fibers  of  posterior  root. 

4.  Fibers  that  enter  the  posterior  horn, 
k,  k.   Collaterals  of  antero-posterior  column. 

1,  1.      Collaterals  from  the  pyramidal  tracts. 

columns.  Commissural  cells  give  off  axis-cylinder  processes  to  the 
opposite  side  of  the  cord,  by  way  of  the  anterior  gray  commissure. 
The  axis -cylinders  of  some  ganglion -cells  terminate  in  the  gray 
matter  itself.  The  fibers  of  the  posterior  nerve-roots,  arising  from 
the  cells  of  the  spinal  ganglia,  divide  into  ascending  and  descend- 
ing branches,  which  enter  the  posterior  columns. 

The  difficulties  in  the  way  of  tracing  the  paths  of  the  fibers 
in  the  cord  are  enhanced  by  the  numerous  collaterals  arising 
from  many  axis -cylinders. 


THE  BRAIN  AND   ITS   MEMBRANES  235 


THE  BRAIN  AND  ITS  MEMBRANES 

le  brain  and  spinal  cord  are  surrounded  by  three  connective 
tissue  layers — the  dura  mater,  the  arachnoid,  and  the  pia  mater. 

The  dura  mater  is  the  most  external  and  the  thickest  of  the 
three  membranes,  and  constitutes  the  periosteal  lining  of  the  cranial 
cavity.  It  consists  largely  of  elastic  tissue,  the  laminae  and  blood- 
vessels of  which  are  supported  by  connective  tissue.  The  outer 
surface  is  in  more  or  less  intimate  connection  with  the  bone  ;  the 
inner  surface  is  covered  with  a  single  layer  of  thin  endothelial 
cells.  Beneath  is  a  space — the  subdural — containing  lymph. 

The  arachnoid,  exceedingly  thin,  presents  an  outer  glistening 
surface,  covered  with  a  layer  of  endothelial  cells.  It  is  devoid  of 
blood-vessels  and  nerves.  It  is  separated  from  the  dura  by  the 
subdural  space,  from  the  under  (inner)  side  of  which  short, 
fibrous  trabeculaa  are  projected  to  the  pia.  Other  trabeculaa 
attach  it  loosely  to  the  dura  mater.  Villous  projections  from  the 
arachnoid  enter  the  subdural  space.  Near  the  longitudinal  fis- 
sure they  are  large  and  encroach  upon  the  dura  mater,  forming 
the  Paccliionian  bodies.  The  subaraclinoidal  space  is  thus  seen 
to  consist  of  numerous  communicating  chambers,  and  these 
spaces  are  everywhere  lined  with  flat  cells,  and  contain  lymph, 
as  does  the  subdural  space. 

The  pia  mater  consists  of  fibrillated  connective  tissue,  usually 
in  intimate  connection  with  the  arachnoid  externally,  by  means  of 
the  trabeculae  of  the  latter.  The  pia  mater  is  exceedingly  vas- 
cular, and  everywhere  covers  the  brain  and  cord;  and,  unlike  the 
arachnoid,  penetrates  the  sulci  of  the  former  and  the  fissures  of 
the  latter,  becoming  continuous  with  the  connective  tissue.  The 
outer  surface  of  the  pia  mater  is  also  covered  with  flat  eriftothe- 
lial  cells. 

The  subdural  and  subaraclinoidal  spaces  are  lymph -cavities,  and, 
while  not  in  direct  connection  one  with  the  other,  belong  to  the 
general  lymphatic  system,  and  are  in  eventual  connection. 

The  arrangement  of  gray  and  white  nerve -substance  in  the 
brain  is  precisely  the  reverse  of  that  of  the  cord.  The  gray 
matter  forms  an  external  covering  or  layer  of  varying  thickness, 
while  the  white  matter  occupies  the  more  central  regions.  Collec- 
tions of  gray  matter— the  basal  ganglia — are  also  situated  in  the 


236 


STUDENTS   HISTOLOGY 


deeper  parts  of  the  brain -substance,  the  study  of  which  does  not 
come  within  the  limits  of  this  work. 

The  brain -substance  does  not  differ  essentially  from  the  cord, 
except   in   the  arrangement  of   its  parts.      The   nerve -fibers   are 


I  iM-i 

,j  ntL  ii ,  n  )• 


FIG.   153.     LAYERS  OF  THE  HUMAN  CEREBRAL,  CORTEX.     (MEYNERT.) 
The  numbers  refer  to  the  layers  given  in  the  text,  page  238. 

mostly  medullated,  but  have  no  neurilemma.  The  gray  substance 
is  arranged  in  five  layers,  which  are  in  some  instances  quite 
sharply  defined,  and  oftener  demonstrable  only  with  considerable 
difficulty.  Transversely  running  bands  of  medullated  nerve -fibers 


THE    CEREBRUM 


237 


(the  stripes  of  Baillarger)  have  sometimes  been  counted  as  addi- 
tional layers. 

PRACTICAL    DEMONSTRATION 

The  tissue  is  to  be  prepared  in  the  manner  usual  with  nerve -substance 
—hardened  with  Miiller,  followed  by  alcohol.  Thin  sections,  stained  deeply 
with  haematoxylin  and  eosin,  may  be  mounted  in  balsam.  Sections  stained 
by  Golgi's  method  should  be  studied  if  possible. 


SECTION    OF    HUMAN    CEREBRUM— CUT    PERPENDICULARLY 
TO    THE    SURFACE    (Fig.  154) 

OBSERVE  : 
(L.) 

The  membranes.  (In  the  drawing  only  the  arachnoid  and  pia 
are  shown.)  (a)  The  fine  fibrillar  mesh  of  the  arachnoid. 
(&)  The  nuclei  of  the  flattened  cell-covering,  (c)  The  large 


Fia.  154.    VERTICAL,  SECTION  OF  CEREBRAL  CORTEX.     SUPERIOR  FRONTAL 
CONVOLUTION  (X  250). 

A.  Arachnoid. 

B.  Pia  mater. 

1,  2,  3,  4,  5.   First,  second,  third,  fourth,  and  fifth  layers  of  gray  matter. 
6.   White  matter. 


238  STUDENTS   HISTOLOGY 

blood-vessels.     00  The  pia.     (e)  Its  continuity  with  the  con- 
nective tissue  of  the  cerebrum. 

1.  The  outer  layer — the  first — of  the  gray  substance.     (This 
layer  is  poorly  defined,  but  can  usually  be  made  out.     It  consists 
of  primitive  nerve -fibrillae,   neuroglia -fibrils,  and   scattered  gan- 
glion-cells.     A    few    medullated    nerve -fibers    run     horizontally 
— tangential  fibers.) 

2.  The  second   layer.     (This  layer  presents  about  the  same 
thickness  as  the  preceding,  and  will  be  recognized  by  the  abun- 
dance of  small  triangular  nerve -cells.     From  Golgi  preparations 
it  appears  that  numerous  protoplasmic  processes  pass  peripherally, 
while    the  axis -cylinders    arise    from    the    bases    of    the    small 
pyramidal   ganglion-cells.) 

3.  The  third  layer.     (This  layer— the  thickest  of  all  the  gray 
laminae — is  called   the  formation  of   the  cornu   Ammonis    [Mey- 
nert] .       The  large  pyramidal  cells  have  numerous  protoplasmic 
processes  arising  from  their  sides  and  prominent  ones  from  the 
apices,  while  the  axis -cylinders  are  given  off  from  the  blunt  bases 
to  enter  the  white  matter  [Fig.  155] .     Medullated  fibers,  in  more 
or  less  distinct  bundles,  pass  between  the  column -like  ganglion- 
cells.) 

4.  The  fourth  layer.     (The  large  cells  of  the  third  layer  are 
seen  to  stop,  as  we  pass  inward,  and  give  place  to  small,  irregu- 
lar nerve -cells,  called  the  granular  formation.     Between  the  cells 
of   this  layer   bundles  of   nerve -fibers  are  seen,  as  they  radiate 
toward  the  cerebral  surface.) 

5.  The  fifth  layer.     The  line  of  demarcation  between  this  and 
the  fourth  layer  is  feebly  shown;   but,  on  close  attention,  it  will  be 
observed  that  the  small  cells  of  the  fourth  layer  rather  abruptly 
give  place  to  spindle-shaped  ones,  sometimes  parallel  with  the  sur- 
face.    The  nerve-bundles  are  here  more  plainly  indicated. 

6.  The  white  matter.     (The  ganglion -cells  cease  here,  and  the 
field  is  occupied  with  medullated  fibers  and  neuroglia,  the  spherical 
nuclei  of  the  latter  becoming  prominent  from  the  deep  haematoxy- 
lin  staining.) 

7.  The    nutrient    blood-vessels.     (The    capillaries    projected 
from  the  pia  are  especialty  to  be  noticed,  often  of  the  diameter  of  a 
single  blood -corpuscle,  and  appearing  as  branching  lines,  composed 
of  these  elements — indeed  difficult  of  demonstration  when  empty. 
Note  the  light,  perivascular  lymph -spaces,  well  seen  around  the 
larger  arteries  in  transverse  section.) 


THE    CEREBRUM 


239 


Certain  concentrically  striated  bodies,  corpora  amylacea,  are 
often  found  in  the  vicinity  of  the  ventricles  and  along  the  olfac- 
tory tract,  as  well  as  in  other  localities.  After  treatment  with 
iodine  solution  and  sulphuric  acid  they*  take  a  violet  color,  there- 
fore resembling  starch  in  their  reactions — hence  their  name. 

The  arrangement  of  the  layers  of  the  gray  matter  is  subject  to 
considerable  modification  in  different  parts  of  the  cerebrum.  As 
in  the  spinal  cord,  the  difficulties  of  tracing  the  course  of  the  nerve- 


FIG.  155.    PYRAMIDAL  GANGLION-CELL  AND  NEUROGLIA-CELL  FROM  HUMAN  CERE- 
BRAL CORTEX  PREPARED  BY  THE  GOLGI  METHOD. 

a.  Axis-cylinder  process  of  the  ganglion-cell. 


fibers  are  increased  by  the  numerous  collaterals  given  off  from  the 
axis -cylinder  processes  of  the  ganglion -cells. 

The  paths  followed  by  the  fibers  of  the  white  matter  are  very 
complicated.  The  tracts  have  been  mapped  out  largely  by  prepa- 
rations made  by  Weigert's  method  and  its  modifications.  In  gen- 
eral these  fibers  may  be  divided  into  three  groups: 

a.  Projection  fibers,  which  constitute  the  corona  radiata,  pass- 
ing from  the  peduncles  of  the  cerebrum  and  the  basal  ganglia  to 
the  cortical  gray  matter. 

b.  Association  fibers,  which  bring  parts  of  the  same  hemis- 
phere into  relation  with  one  another. 

c.  Commissural  fibers,  which  connect  the  opposite  hemispheres 
through  the  corpus  callosum  and  the  anterior  commissure. 


240  STUDENTS   HISTOLOGY 

VERTICAL    SECTION    OF    HUMAN    CEREBELLUM 
Practical  Demonstration 

Cut  large  sections  of  cerebellum,  hardened  with  Miiller's  fluid  and  im- 
bedded as  usual  ;  cut  so  as  to  show  the  ramifications  of  the  arbor  vita? ;  stain 
with  haematoxylin  and  eosin.  Also  stain  the  cerebellum  of  a  young  dog  or 
kitten,  prepared  according  to  Golgi's  method  (page  33),  being  careful  to  cut 
the  sections  at  a  right  angle  to  the  long  axis  of  the  convolutions. 

OBSERVE  :  (Fi«s- 156  and  157> 

(L.) 

1.  The  arrangement  in  the  form  of  leaflets. 

2.  The  extension  of   the  gray  laminae  within  even  the  mi- 
nutest folds  of  the  leaves,  so  as  to  completely  envelop  the  central 
white  nerve -substance.     (The  staining  has  been  so  selected  by  the 


FIG.  156.  LONGITUDINAL  SECTION  OF  ONE  OF  THE  FOLIA  OF  THE  CEREBELLUM  (X60). 

A,  A.   Line  of  pia  mater. 

B,  B.   Sulci. 

C,  C.    Outer  layer  of  gray  matter. 

D,  D.  Inner  layer  of  gray  matter,  including  Purkinje's  cells. 

E,  E.   White  nerve-substance. 


THE  CEREBELLUM 


241 


FIG.   157.    VERTICAL  SECTION,  CORTEX  OF  CEREBELLUM.    PORTION  OF  SECTION 
SHOWN  IN  FIG.   156,  MOKE  HIGHLY  MAGNIFIED  (X  250). 

A.  Outer  layer  of  gray  matter. 

B.  Layer  of  Purkinje's  cells. 

C.  Inner  gray  layer. 

D.  White  nerve-substance. 

tissue  as  to  divide  the  outer  gray  matter  into  two  prominent  layers. 
The  explanation  of  this  will  follow  increased  amplification.) 

3.  The  central  white  matter.     (The  fibrillar  character  can  be 
made  out,  and  the  general  plan  will  be  found  to  consist,  as  in  the 
cerebrum,  of  central   nerve -fibers   radiating   toward   the  cells  of 
the  cortical  gray  substance,  the  arbor  vitae.) 

(H.) 

4.  The  outer  gray  layer,  or  molecular   layer.       (This  is  the 
thickest  of  the  three  layers.     The  prominent  elements  to  be  ob- 
served are  :   the  scattering  neuroglia-  and  ganglion-cells,  nerve- 
fibrils,  and  blood-vessels,  which  pass  in  from   the   pial   invest- 
ment.)     The    ganglion -cells  of   the   molecular   layer  are  of   two 
sorts,  small  and  large.     The  large  cells  are  remarkable  for  their 
axis -cylinder  processes,  which  at  intervals  give  off  branches  whose 


242 


STUDENTS   HISTOLOGY 


fine  subdivisions  form  a  basket-like  network  about  the  bodies  of 
the  Purkinje  cells  of  the  underlying  layer.  The  arborizations  of 
these  Purkinje  cells  spread  out  in  the  molecular  layer. 

5.  The  middle  layer  is  a  thin  stratum  directly  beneath  the 
outer  layer.  The  section  becomes  deeply  stained,  from  the  pres- 
ence of  numerous  small  cells,  among  and  partly  concealed  by 
which  are  the  very  large  ganglion-cells  of  Purkinje.  These  are 
flask -shaped,  and  are  arranged  in  a  single  plane,  with  their  long 
axes  placed  vertically.  A  thread-like  prolongation  may  be  seen 


FIG.  158.     CELL  OF  PURKINJE.    HUMAN  CEREBELLUM.    GOLGI  METHOD. 

penetrating  the  layer  beneath,  providing  the  cell  has  been  cen- 
trally sectioned.  This  is  the  axis -cylinder  process,  which  gives  off 
certain  collaterals  and  becomes  the  axis -cylinder  of  a  medullated 
nerve -fiber.  Two  thick  protoplasmic  processes  project  from  the 
outer  end  of  the  cell,  which  ramify  in  the  molecular  layer.  Their 
arborizations  are  luxuriant,  and  the  branchings  of  the  various  cells 
have  been  likened  to  a  forest.  Considering  the  large  size  of  the 
cells  of  Purkinje,  their  axis -cylinder  processes,  the  richness  of  the 
branches  of  their  protoplasmic  processes,  and  the  curious  basket- 
work  of  nerve -fibrils  around  the  cell -bodies,  they  are  among  the 


THE    CEREBELLUM  243 

most  striking  of  the  objects  that  have  been  revealed  by  the  Golgi 
method.     (Fig.  158.) 

The  branches  of  these  cells  spread  out  chiefly  on  planes  at  right 
angles  to  the  long  axis  of  the  convolution.  Sections  should  there- 
fore be  made  across  the  convolutions. 

6.  The  granular  layer.     (This  is  the  layer  seen  so  distinctly 
with   the   low -power.      It  consists  of   innumerable  small   bodies, 
deeply   stained   with   haematoxylin,   usually   spherical,  which   are 
ganglion-  and  neuroglia- cells.     The  ganglion -cells  belong  to  the 
second  type.     The  majority  of  these  cells  are  small.     A  few  are 
large.     The  small  cells  have  protoplasmic  processes  Which  ramify 
in  their  own  granular  layer,  and  axis -cylinders  which  terminate  in 
the  outer  molecular  layer.     On  the  other  hand  the  large  ganglion - 
cells   of   the    granular   layer   have   protoplasmic   processes  which 
extend  into  the  molecular  layer,  while  the  axis -cylinder  processes 
ramify  in  the  granular  layer.     Medullated  nerve -fibers  from  the 
white  matter  form  a  dense  plexus  in  the  granular  layer.     Some  of 
these  fibers  are  continued  into  the  molecular  layer.     Search  care- 
fully for  the  axis-cylinder  processes  of  the  Purkinje  cells,  which 
pierce  this  layer,  and  follow  them  into  the  white  matter  below.) 

7.  The  white  substance  consists  of  medullated  nerve -fibers. 


INDEX 


Abbe"  condenser,  1,  4. 

Abdominal  cavity.     See  Peritoneum. 

salivary  gland,  145. 
Absorption  from  intestine,  158. 

of  fat,  159. 
Acid,  acetic,  39. 

alcohol,  29,  39. 
aniline  dyes,  31. 
chromic,  24. 
fuchsin,  31,  32. 
hydrochloric,  25,  29,  39. 
nitric,  24,  75,  137. 
osmic,  23. 

picric,  23,  29,  31,  32. 
Acidophile  granules,  31. 
Acini  of  glands,  140. 
Acinous  glands,  143. 
Acoustic  nerve,  216. 
Adenoid  reticulum,  76,  113. 

tissue,   76,   111.      See   Lymphoid 

tissue. 
Adipose  tissue,  65. 
Adventitia  of  blood-vessels,  103,  104. 
Agents,  staining,  27. 
Agminate  glands,  160. 
Ailantus  pith,  13. 
Air-bubbles,  46. 
-sacs,  128. 
-vesicles,  128. 
Alcohol,  acid,  29,  39. 

fixation  and  hardening,  21. 
dehydration  with,  35,  38. 
Alimentary  canal,  149. 
Alum-ha3matoxylin,  28. 
Alveoli  of  gland,  140. 

of  lung,  128. 

Amoeboid  movements,  83,  104. 
Amphophile  granules,  31. 
Aniline  colors,  dyes,  etc.,  31. 
dyes,  staining  with,  31. 
oil,  35. 
Anterior  commissure,  227. 

median  fissure,  227. 
Antero-lateral  tracts,  228. 
Aorta,  104. 
Appendages  of  skin,  95. 


Appendix,  vermiform,  162. 
Aponeuroses,  62. 
Arachnoid,  235. 
Arbor  vitro,  241. 
^.reolar  tissue,  62. 
Arrectores  pili,  96. 
Arrowroot-starch,  48. 
Arteries,  102. 

large,  103,  104. 
lymphatics  of,  107. 
small,  103. 

Arteriolae  rectee  of  kidney,  184. 
Arterioles,  102. 
Artery,  bronchial,  128. 

hepatic,  164. 

pulmonary,  128. 

renal,  183. 

typical,  103. 
Articular  cartilage,  68. 
Artificial  gastric  juice,  25. 
Asphaltum  varnish,  36. 
Association  fibers,  239. 
Attraction-spheres,  53. 
Auerbach's  plexus,  154,  160. 
Axis-cylinder,  216.. 

processes,  220. 
collaterals,  222. 

Bacteria,  hardening  tissues  containing,  22. 

under  the  microscope,  47. 
Baillarger's  stripes,  237. 
Balsam,  Canada,  35. 
Basement  membranes,  55. 
Basic  aniline  dyes,  31. 
Basophile  granules,  31,  87. 
Beaker  cells.     See  Goblet  cells. 
Bellini,  tubule  of,  182. 
Bergamot  oil,  35. 
Bertini,  columns  of,  179. 
Berlin  blue,  injecting,  34. 
Bichromate  of  potassium,  22. 
Bile-capillaries,  166. 

-ducts,  injection  of,  176,  177. 
Bipolar  nerve-cells,  220. 
Birds,  blood  of,  82. 
Bladder,  gall-,  177.  f 


(245) 


246 


INDEX 


Bladder,  urinary,  194. 
Blastodermic  layers,  j54. 
Blood,  81. 

colorless  corpuscles,  83. 

-corpuscles  as  a  standard  of  meas- 
urement, 8. 

-corpuscles,    cover-glass    prepara- 
tions, 84. 

-corpuscles,  crenation  of,  82,  90. 

-corpuscles,  double  staining,  84. 

-crystals,  89. 

effect  of  reagents  upon,  90. 
.    effects  of  acetic  acid,  91. 

effects  of  osmic  acid,  82. 

effects  of  tannic  acid,  91. 

effects  of  water,  90.  [32,  85. 

Ehrlich-Biondi-Heidenhain    stain, 

embryonal  origin  of,  91. 

enumeration  of  corpuscles,  87. 

fibrin,  90. 

fixing  and  staining,  84. 

haemin,  90. 

haemoglobin,  89. 

haemosiderin,  89. 

haematoidin,  89. 

human,  81. 

leucocytes,  83. 

of  birds,  82. 

of  camelidae,  82. 

of  fishes,  82. 

of  frog.  90. 

of  invertebrates,  82. 

of  lamprey,  91. 

of  reptiles,  82. 

origin  of  colored  corpuscles,  91. 

origin  of  white  corpuscles,  87. 

oxygenation  of,  89. 

-plates,  82. 

red  corpuscles,  81. 

size  of  corpuscles,  81. 

tricolor  or  triacid  stain,  32,  85. 

-vessels,  102. 

-vessels,  capillary,  103. 

-vessels,  development  of,  105. 

-vessels,  injection  of,  34. 

white  corpuscles,  83. 
Bodies,  Malpighian  of  kidney,  180. 
Malpighian  of  spleen,  118. 
Pacchionian,  235. 
suprarenal,  213. 
thymus,  121. 
thyroid,  148. 
of  Langerhans,  148. 
Bone,  70. 

circumferential  lamellae,  72. 


Bone,  compact,  72. 

cancellous,  72. 

-corpuscles,  72. 

decalcification  of,  24,  75. 

development  of,  73. 

Haversian  canals,  71. 

Haversian  lamellae,  72. 

interstitial  lamellae,  72. 

-lacunae,  70. 

-marrow,  73. 

osteoblasts,  73. 

osteoclasts,  73. 

perforating  fibers  of  Sharpey,  71. 

periosteum,  73. 

spongy,  72. 

varieties  of,  72. 
Borax-carmine,  29,  39. 
Boundary  region  of  kidney,  187. 
Bowman,  capsule  of,  180. 
Bowman's  muscle-disks,  80. 
Brain,  235.     See  Cerebrum. 
Branched  tubular  glands,  143. 
Bronchial  artery,  128. 

tube,  123. 
Bronchi,  123. 
Bronchus  of  pig,  125. 
Brownian  movements,  46. 
Brunner's  glands,  157. 
Bubbles,  air-,  46. 
Buccal  epithelium,  56,  149. 
glands,  143. 
cavity,  149. 
Burdach's  column,  228. 

Calcified  cartilage,  74. 
Calcification,  73. 
Calyces  of  kidneys,  178. 
Canada  balsam,  35. 
Canal,  alimentary,  149. 
central,  227. 
dentinal,  135. 
Haversian,  71. 
of  the  epididymis,  210. 
portal,  165. 
Canaliculi,  70. 
Cancellous  bone,  72. 
Capillaries,  blood-,  103. 
bile-,  166. 

lymphatic,  106-110. 
Capillary  bronchial  tubes,  123. 
Capsule  of  Bowman,  180. 
of  glands,  140. 
of  Glisson,  163. 
of  kidney,  178. 
of  lymph-nodes,  112. 


INDEX 


247 


Capsule  of  spleen,  117. 

of  thymus  body,  121. 
suprarenal,  213. 
Carbol-turpentine,  35. 

-xylol,  35. 

Carbon  dioxide  freezing,  20. 
Cardiac  glands,  152. 

muscle-fiber,  80. 
Care  of  miscrocope,  43. 
Carmine  and  picric  acid,  29. 

Grenadier's  borax-,  29. 
injection,  34. 
staining,  39. 
Cartilage,  67. 

articular,  68. 
arytenoids,  123. 
-corpuscles,  67. 
elastic,  68,  123. 
fibro-,  68. 
hyaline,  67. 
-lacunae,  67. 
of  epiglottis,  123. 
of  larnyx,  123. 
of  Santorini,  123. 
of  trachea,  68,  123. 
of  Wrisberg,  123. 
perichondrium  of,  67. 
-plates  in  bronchi,  124. 
reticular,  68,  123. 
varieties  of,  67. 
Cavity,  abdominal.     See  Peritoneum, 
pericardial.     See  Pericardium, 
thoracic  or  pleural.     See  Pleura. 
Cedar-wood  oil,  4. 
Cell,  49. 

-cement,  50. 
distribution,  50. 
division,  51. 
typical,  49. 
-wall,  49. 

Celloidin  imbedding,  26. 
Cells,  acidophile,  31. 
amphophile,  31. 
basophile,  31,  87. 
bipolar  nerve-,  220. 
blood-,  81. 
border,  153. 
central,  153. 
chief,  153. 
Deiter's,  222. 

endothelial.     See  Endothelium. 
eosinophile,  31,  86. 
epithelial.     See  Epithelium, 
ganglion-,  219. 
giant.     See  Giant  cells. 


Cells,  goblet.     See  Goblet  cells. 

lymphoid.     See  Lymphoid  cells, 
mucous.     See  Goblet-cells, 
multipolar  nerve-,  220. 
nerve-,  219. 
neutrophile,  31,  86. 
neuroglia,  222. 
of  Purkinje,  242. 

outlining  of  by  silver  nitrate,  33,  60. 
parietal,  153. 
pigment-,  93. 
prickle,  92. 
spider,  222. 
typical,  49. 
unipolar  nerve-,  220. 
wandering,  83,  104. 
Cement-substance,  62,  104,  108. 
of  tooth,  137. 
zinc,  36. 

Central  canal  of  spinal  cord,  227. 
nervous  system,  226-243. 
Centrosome,  53. 
Cerebellar  tracts,  direct,  228. 
Cerebellum,  240. 

cells  of  Purkinje,  242. 
granular  layer,  243. 
molecular  layer,  241. 
Cerebral  cortex,  layers  of,  238. 
Cerebrum,  236. 

association  fibers,  239. 
blood-vessels,  238. 
commissural  fibers,  239. 
nerve-fibers  of,  239. 
practical  demonstration,  237. 
projection  fibers,  239. 
tangential  fibers,  238. 
pyramidal  cells  of,  238. 
Cervix  uteri,  198. 
Chalice  cells.     See  Goblet  cells. 
Chamois  leather,  43. 
Channels,  lymph-.     See  Lymphatics, 
blood-.     See  Blood-vessels. 
Chloroform,  25. 
Chromatin,  28,  51. 
Chromosomes,  52. 

Chromic  acid,  fixing  and  hardening,  24. 
Chromic-acetic  solution  of  Flemming.  23. 
-osmic   solution  of    Flem- 
ming, 23. 

Chyle-receptacle,  106. 
Ciliary  motion,  59. 
Ciliated  cells  from  oyster,  59. 
Circulatory  system,  102. 

system,  lymphatic,  106. 
Circumferential  lamellae,  72. 


248 


INDEX 


Circumvallate  papillae,  149. 
Clark's  columns,  232. 
Classification  of  tissues,  53.  • 
Cleaning  cover-glasses,  41. 

lenses,  44. 

Clearing  agents,  35,  38. 
Clove-oil,  35. 
Coarse  adjustment,  1. 
Cohnheim's  fields,  79. 
Coiled  tubular  glands,  140. 
Collaterals  of  axis  cylinders,  222. 
Collecting  tubule,  182. 
Collodion,  26. 
Colloid  substance,  148. 
Colorless  blood-corpuscles,  83,  104. 
Colors,  aniline,  31. 
Colostrum-corpuscles,  208. 
Columns  of  the  spinal  cord.     See  Spinal 

cord. 

Columnar  epithelium,  57. 
Columns,  cortical,  of  Bertini,  179. 
Commissural  fibers,  239. 
Commissure,  anterior  gray,  227. 
posterior  gray,  227. 
white,  228. 
Compact  bone,  72. 
Compound  acinous  glands,  143. 

racemose  glands,  143. 
Condenser,  Abbe,  1,  4. 
Coni  vasculosi,  210. 
Connective  tissue,  62. 

tissue,  embryonic,  76. 
tissue,  juice-canals  of,  106. 
tissue,  mucoid,  76. 
tissue,  special,  76. 
Conservation  of  eyesight,  7. 
Constrictions  of  Ranvier,  216. 
Convoluted  tubule,  181,  182. 
Copper  sulphate,  24. 
Cord,  spinal.     See  Spinal  cord. 

umbilical,  76. 

Cords  of  lymphoid  tissue,  113. 
Corium  of  skin,  92. 
Corn  starch,  48. 
Cornea,  nerves  of,  223. 
Cornua  of  spinal  cord,  227. 
Corpora  amylacea  of  brain,  239. 
Corpus  callosum,  239. 
Highmori,  210. 
luteum,  203. 
Corpuscles,  blood-,  81. 
bone-,  70. 
cartilage-,  67. 
colostrum-,  208. 
connective  tissue,  63. 


Corpuscles,  Hassall's,  122. 

lymph-.     See  lymphoid  cells. 

of  Vater,  223. 

pus-,  84. 

Pacinian,  223. 

salivary,  47,  149. 

tactile,  94,  223. 
Cortex  of  cerebellum,  241. 
of  cerebrum,  237. 
of  ovary,  203. 
of  kidney,  178. 
of  lymph-node,  112. 
of  thymus  body,  121. 
Cortical  columns  of  kidney,  179. 
Corundum  hones,  16. 
Cotton  fibers,  48. 
Cover-glasses,  41. 
Cover-glass,  placing  of,  42. 

preparations  of  blood,  84. 
Cox's  Golgi  method,  34. 
Crenation  of  blood-corpuscles,  82. 
Creosote,  35. 

Crossed  pyramidal  tracts,  228. 
Crusta  petrosa,  135. 
Crypts  of  the  tonsil,  149. 

of  Lieberkuhn,  156. 
Crystals  of  Teichmann,  90. 
Cul-de-sac  of  vagina,  198. 
Currents,  thermal,  46. 
Cuticle  of  hairs,  95. 
Cutis  anserina,  96. 
Cuticula  of  tooth,  135. 
Cutting  sections,  10. 
Cylinder,  axis-,  217. 
Cyclostomi,  blood  of,  91. 

Dammar,  36. 
Decalcification,  24. 

of  bone,  75. 
of  teeth,  137. 
Dehydrating,  35,  38. 
Deiter's  cells,  222. 
Delafield's  hsematoxylin,  28. 
Demilunes  of  Heidenhain,  148. 
Demonstrations,  practical.     See  Practical 

demonstrations. 
Dendrites,  220. 
Dentinal  canals,  135. 
fibers,  135. 
sheath,  135. 
Dentine,  135. 

Derivatives  of  blastodermic  layers,  54. 
Derma,  92. 

basement  membrane,  of,  94. 
Development  of  blood-vessels,  105. 


INDEX 


249 


Development  of  blood-corpuscles,  91. 

of  bone,  73. 
Diapedesis,  104. 

Diaphragm,  central  tendon  of,  108. 
Diaphragm  of  the  microscope,  1. 
Direct  cell  division,  51. 
Direct  cerebellar  tract,  228. 
Direct  pyramidal  tract,  228. 
Digestion,  method  of,  25. 
Disk,  intervertebral,  68. 

of  Bowman,  80. 
Discus  proligerus,  205. 
Dissociating  fluids,  10,  25. 
Distal  convoluted  tubule,  182. 
Distribution,  cell,  50. 
Division  of  cells,  51. 
Double  staining,  38. 
Duct  of  glands,  140. 

hepatic,  163,  177. 

of  thyroid  body,  148. 

bile-,  176,  177. 

thoracic,  106,  107. 
Ductless  glands.  117,  213. 
Dura  mater,  235. 
Dust  on  lenses,  43. 
Duodenum,  162. 

Ear,  cartilage  of,  68. 
Ectoderm,  derivatives  of,  54. 
Egg-tubes,  206.  [32. 

Ehrlich-Biondi-Heidenhain  tricolor  stain, 
Elastic  cartilage,  68. 

fibers,  65. 

lamina  of  blood-vessels,  102,  103. 

tissue,  63. 
Elder-pith,  13. 
Eleidin,  92. 

Embedding.     See  Imbedding. 
Embryonic  tissue,  76. 
Enamel  of  teeth,  137. 

prisms,  137. 
Endocardium,  102. 
Endochondral  formation  of  bone,  73. 
Endomysium,  78. 
Endoneurium,  218. 
Endothelial  cells.     See  Endothelium. 
Endothelium,  60,  103,  108. 

of  blood-vessels,  103. 
staining  of,  61. 
stomata  of,  62. 
End-plates,  225. 
Entoderm,  derivatives  of,  54. 
Eosin,  28,  31. 

and  haematoxylin,  38. 
Eosinophile  granules,  31,  86. 


Epiblast,  derivatives  of,  54. 

Epidermis,  92. 

Epididymis,  209. 

Epiglottis,  68,  123. 

Epineurium,  218. 

Epithelial  cells.     See  Epithelium. 

Epithelium,  definition  of,  54. 

buccal,  56. 

ciliated,  58. 

classification  of,  55. 

columnar,  57. 

distribution  of,  55. 

germinal,  203. 

glandular,  59. 

of  bladder,  195. 

of  ovary,  203,  206. 

of  kidney,  182,  192. 

pavement,  56. 

prickle  cells,  92. 

simple  squamous,  56. 

stratified,  55. 

striated,  148,  192. 

squamous,  55. 

tessellated,  56. 

transitional,  55,  193,  195. 

uterine,  199. 

vaginal,  200. 

varieties  of,  55. 
Equator  of  the  cell,  52. 
Erectile  tissue,  212. 
Erlicki's  fluid,  24. 
Erythroblasts,  91. 
Ether  freezing,  20. 
Eustachian  tube,  cartilage  of,  68. 
Extraneous  substances,  47. 
Eye-lens,  3. 
-piece,  3. 

Fallopian  tube,  202. 

Fat,  action  of  osmic  acid  on,  23. 

-cells,  65. 

-columns,  94. 

-crystals,  66. 

-globules  in  milk,  45. 

in  the  liver,  174. 

staining  of,  23. 

-tissue,  65. 
Feathers,  48. 

Female  generative  organs,  197. 
Fenestrated  membrane,  05,  103. 
Ferrein,  pyramids  of,  179. 
Fibers,  association,  239. 
commissural,  239. 
cotton,  47. 
dentinal,  135. 


250 


INDEX 


Fibers,  linen,  47. 

nerve-,  216. 

perforating  of  Sharpey,  71. 
projection,  239. 
silk,  47. 
tangential,  238. 
wool,  47. 
Fibrin,  90. 
Fibro-cartilage,  68. 
Fibrous  tissue,  elastic,  63. 
white,  62. 
Field  lens,  3. 

of  view,  5. 
Filiform  papillae,  149. 
Fine  adjustment,  1,  6. 
Fishes,  blood  of,  82,  91.  [227. 

Fissure,  anterior  median,  of  spinal  cord, 
posterior  median,  of  spinal  cord, 
Fixation  of  tissues,  20.  [227. 

Fixing  blood-elements,  84. 

fluids,  etc.,  20. 
Flemming's  solutions,  23,  24. 
Fluid,  artificial  gastric,  25. 
dissociating,  10,  25. 
Erlicki's,  24. 
Flemming's,  23. 
Miiller's,  22. 
Orth's,  22. 
Stirling's,  25. 
Toison's,  87. 
Focal  adjustment,  5. 
Focusing,  5,  45. 
Foetal  blood,  91. 

blood-vessels,  105. 
bone,  73. 
lung,  134. 

Follicle  of  hair,  95. 
Follicles,  Graafian,  203. 

of  Lieberkiihn,  156. 
of  lymphoid  tissue,  113. 
solitary,  160. 
Foramen  caecum,  148. 
Formaldehyde,  22. 
Form  of  objects,  45. 
Free  nerve-endings,  223. 
Freezing  microtome,  19. 
Fresh  tissue,  20. 
Frog,  blood  of,  90. 

capillaries  of,  105. 
mesentery  of,  60. 
skin  of,  56. 
Fuchsin,  31. 

acid,  31,  32. 

Fungiform  papillae,  149. 
Funiculus  cuneatus  of  spinal  cord,  228. 


Funiculus  gracilis  of  spinal  cord,  228. 
Funiculi  of  nerve-trunks,  217 

Gall-bladder,  177. 

-duct,  177. 
Ganglia  of  heart,  102. 

of  urinary  bladder,  195. 
Ganglion-cells.  See  Nerve-cells. 
Gastric  fluid,  artificial,  25. 

glands,  152. 

tubules,  152. 
Generative  organs,  female,  197. 

male,  209. 
Gentian  violet,  31. 
Germinal  epithelium,  203. 
spot,  205. 
vesicle,  205. 
Giant  cells,  73,  120. 
Glands,  140. 

acinous,  143. 

agminate,  160. 

branched  tubular,  143. 

Brunner's,  157. 

buccal,  143. 

capsule  of,  140. 

cardiac,  152. 

coiled  tubular,  140. 

compound  racemose,  143. 

compound  tubular,  143. 

ductless.     See  Ductless  glands. 

gastric,  152. 

intestinal,  156,  157. 

Lieberkuhn,  156. 

lenticular,  156. 

Littre',  196. 

lymphatic.    See  Lymphatic  nodes. 

mammary,  208. 

mucous.     See  Mucous  glands. 

mucous,  of  bronchi,  127. 

Nabob's,  199. 

pancreas,  145. 

parenchyma  of,  140. 

parotid,  143. 

peptic,  152. 

Fever's,  160. 

pyloric,  152. 

racemose,  143. 

salivary,  143,  148. 

sebaceous,  98. 

simple  tubular,  140. 

sublirigual,  148. 

solitary,  160. 

submaxillary,  144. 

sudoriferous,  97. 

sweat-,  97. 


INDEX 


251 


Glands,  tubular,  140,  143. 

thyroid,  148. 

Glandular  epithelial  cells,  59. 
Glassy  membrane  of  hair,  95. 
Glisson's  capsule,  163. 
Globus  major,  209. 

minor,  209. 
Globules,  oil-,  46. 
Glomerulus  of  kidney,  184. 
Glycerine  in  mounting,  36,  76. 
Glycogen  in  the  liver,  174. 
Goblet  cells,  58,  126,  127,  157. 
Gold-staining,  33. 
Golgi's  method,  33. 
Goll,  column  of,  228. 
Gowers,  column  of,  228. 
Goose-flesh,  96. 
Graaflan  follicles,  203. 
Gray  commissure,  227. 
Gray  matter  of  brain,  236. 

spinal  cord,  226. 
Grenacher's  borax-carmine,  29. 
Griibler's  dyes,  31. 
Gum  dammar,  36. 
Gun-cotton,  26. 

Haematoxylin,  28. 

and  eosin,  38. 
Delafleld's,  28. 
staining  process,  36. 
Weigert's,  30. 
Hfemin,  90. 
Haemoglobin,  89. 
Haemocytometer,  87. 
Haematoidin,  89. 
Haemosiderin,  89. 
Hair,  95,  99,  101. 

-follicles,  structure  of,  95. 
permanent  mounting  of,  99. 
Hardening,  20. 
Hassall's  corpuscles,  122. 
Haversian  canals,  71. 
lamella,  72. 
system,  71. 
Heart,  80,  102. 

blood-vessels  of,  102. 
endocardium,  102. 
muscular  tissue  of,  80. 
nerves  of,  102. 
pericardium,  102. 
valves  of,  102. 

Heidenhain's  demilunes,  148. 
Henle,  loop  of,  181. 
Hepatic  duct,  163,  177. 
veins,  163. 


Highmori,  corpus,  210. 
Histology,  definition  of,  53. 
Hilum  of  kidney,  178. 

of  lymph-node,  113. 

of  spleen,  117. 
Hones,  16. 

Horns  of  spinal  cord,  227. 
Horny  layer  of  skin,  92. 
Hyaline  cartilage,  67. 
Hypoblast,  derivatives  of,  54. 

Ileum,  section  of,  161. 

Illumination,  4. 

Imbedding  with  ailantus  pith,  13. 

with  celloidin,  26. 

with  paraffin,  13,  25. 
Immersion  lenses,  4. 
Indirect  cell  division,  51. 
Inflammation,  84,  104. 
Infundibula  of  kidney,  178. 

of  lung,  129. 
Injection,  methods  of,  34. 
Insects,  48. 

Intercellular  substance,  50. 
Interglobular  spaces,  137. 
Interlobular  veins  of  liver,  167. 

vessels  of  kidney,  184. 
Intervertebral  disks,  68. 
Interstitial  lamellae,  72. 
Intestines,  151,  156. 

Brunner's  glands  of,  157. 

Lieberkuhn's  follicles  of,  156. 

mucosa  of  large,  162. 

mucosa  of  small,  156. 

Peyer's  patches,  160. 

practical  demonstrations,  160- 

solitary  glands  of,  160.      [162. 

valvulae  conniventes,  151,  162. 

villi  of,  156. 

Intima  of  blood-vessels,  103. 
Intramembranous  ossification,  73. 
Intralobular  vein,  163. 
Involuntary    muscle,    76.      See    Muscle, 

non-striated. 
Iodine  solution,  29. 
Iris  diaphragm,  1. 
Irregular  tubule,  182. 

Japanese  paper,  43. 
Juice,  gastric,  152. 
Jelly  of  Wharton,  76. 
Juice-canals,  106. 

Karyokinesis,  23,  51. 
Keratin,  92. 


252 


INDEX 


Kidney,  178. 

blood-vessels  of,  183. 

boundary  region  of,  187. 

Bowman,  capsule  of,  180. 

calyces  of,  178. 

capsule  of,   178. 

collecting  tubes  of,  182. 

columns  of  Bertini,  179. 

connective  tissue  of,  189. 

cortex  of,  179. 

labyrinth  of,  179. 

diagram  of,  179. 

epithelium,  182,  192. 

Ferrein's. pyramids,  179. 

glomerulus  of,  184. 

Henle's  loop,  181. 

hilum  of,  178. 

infundibula  of,  178. 

labyrinths  of,  179. 

lobules  of,  178. 

Malpighian  bodies  of,  180. 

Malpighian  pyramids,  178. 

medulla,  179. 

medullary  rays  of,  179. 

nerves  of,  185. 

papillae  of,  178. 

pelvis  of,  193. 

practical  demonstration  of,  186. 

tubes  of  Bellini,  182. 

tubules,  diagram  of,  181,  193. 

tubules  of,  180. 
Knives,  sharpening,  16. 
Krause's  membrane,  79. 

Labeling  of  slides,  42. 
Labyrinth  of  kidney,  179. 
Lacteals,  159. 
Lacunae  of  cartilage,  67. 

of  bone,  70. 
Lamellae  of  bone,  72. 
Lamina,  internal  elastic,  103. 
Lamprey,  blood  of,  91. 
Large  intestine,  162. 
Langerhans,  bodies  of,  148. 
Larnyx,  123. 

cartilages  of,  68,  123. 
Lateral  columns,  228. 
Layers  of  cerebrum,  238. 
of  epidermis,  92. 
Lens,  immersion,  4. 

microscope,  2,  3,  4. 
Lenticular  glands,  156. 
Leucocytes,  83,  104. 
Lieberkuhn,  crypts  of,  156. 
Lifting  sections,  41. 


Ligamenta  subflava,  65. 
Ligamentum  nuchae,  65. 
Light  transmitted,  9. 
Limiting  membrane,  49. 
Linen  fibers,  47. 
Lines  of  Retzius,  137. 
Littre",  glands  of,  196. 
Liver,  163. 

cells  of,  174. 
fat  in,  174. 

Glisson's  capsule,  163. 
glycogen  in,  174. 
human,  171. 
of  pig,  167. 
of  rabbit,  174. 

practical  demonstrations,  167,  170, 
scheme  of  structure,  104.  [177. 

Lobes  of  glands,  140. 
Lobules  of  glands,  140. 
Logwood,  27. 
Loop  of  Henle,  181. 
Lung,  123. 

air-sacs,  128. 
blood-vessels  of,  128. 
connective  tissue  of,  128. 
foetal,  134. 
infundibula  of,  129. 
interlobular  septa,  128. 
pigment  within,  128. 
practical  demonstration,  131. 
terminal  bronchiole,  123,  132. 
vascular  supply  of,  128. 
Luschka's  tonsil,  149. 
Lymph,  106. 

-corpuscles,  85,  106. 
-node,  diagram  of,  112. 
-node,  practical  demonstration  of, 
-nodes,  111.  [113. 

-spaces,  106,  107. 
-spaces  of  nerves,  219.  [219. 

-spaces     around      ganglion-cells, 
Lymphatic  capillaries,  106,  110. 
vessels,  107. 

glands.     See  Lymph-nodes, 
system,  106. 

tissue.     See  Lymphoid  tissue. 
Lymphatics,  106,  107. 

practical  demonstration,  108. 
perivascular,  107. 
valves  of,  107,  109. 
Lymphoid  cells,  85,  113. 
tissue,  76,  111. 
tissue,  diffuse,  113. 
tissue    distribution,    113,    118, 

121,  123,  149,  156,  159,  195. 
Lymphocytes,  85. 


INDEX 


253 


Magnification  of  movements,  46. 
Magnifying  power  of  objectives,  7. 
Male  generative  organs,  209. 
Malpighian  stratum  of  epidermis,  92. 
Malpighian  bodies  of  kidney,  180. 

bodies  of  spleen,  118. 
Malpighi,  pyramids  of,  179. 
Mammary  glands,  208. 
Marrow,  bone-,  73. 
Measurement  of  objects,  8. 
Media  of  arteries,  103. 
Mediastinum  testis,  209. 
Medulla  of  bone,  73. 

of  kidney,  179. 
of  lymph-node,  112. 
of  hair,  95. 
of  thymus  body,  121. 
Medullary  cavity  of  bone,  74. 

rays  of  kidney,  179. 
Medullated  nerves,  216. 
Meissner's  plexus,  154,  160. 
Membrana  granulosa,  205.  [branes. 

propria.     See  Basement  mem- 
%lembrane,  basement.        See     Basement 
membranes. 

glassy,  95. 

limiting,  49. 

of  Nasmyth,  135. 

of  Krause,  79. 
Membranes  of  brain,  235. 
Menstruation,  uterus  in,  197. 
Mercuric  chlorid  method  for  nervous  sys- 
tem, 34. 

Mesenteric  lymph-node,  113. 
Mesentery,  silvered,  61. 
Mesoderm  or  Mesoblast,  derivatives  of,  54. 
Methylene  blue,  31,  84. 
Methyl  green,  32. 
Methyl  violet,  87. 
Metric  scale,  8. 
Micro-millimeters,  8. 
Micron,  M,  8. 
Micrometers,  8. 
Microscope,  1. 

adjustment  of,  5. 

care  of,  43. 

illumination,  4. 

magnifying  power  of,  7. 

parts  of,  1. 

sketching  from,  9. 

Microtome,  freezing,  19. 
Minot,  15. 
Schanze,  15. 
Stirling,  12. 
Thoma,  14. 


Milk,  45,  208. 

colostrum-corpuscles,  208. 
fat-globules  in,  45. 
secretion  of,  208. 
Mixed  salivary  glands,  148. 
Mirror,  1,  4. 
Mitosis,  51. 

Molecular  movement,  46. 
Mounting  fluids  and  methods,  35. 

of  objects,  41. 
Mounts,  rings  on,  36,  76. 
Mouth,  149. 

Movement,  Brownian,  46. 
amoeboid,  83. 
vital,  47. 

Movements,  magnification  of,  46. 
Mucoid  tissue,  76. 
Mucosa  of  bronchial  tubes,  123. 

of  stomach  and  intestine,  151. 
of  mouth  and  pharynx,  149. 
of  oesophagus,  150. 
ureter  and  bladder,  193. 
uterus,  199. 
vagina,  199. 
Mucous  glands,  127,  144,  148,  149. 

cells.     See  Goblet  cells. 
Miiller's  fluid,  22. 
Multipolar  nerve-cells,  220. 
Muscular  tissue,  76. 
Muscle,  blood-vessels  of,  80. 
cardiac,  80. 
involuntary,  76.    See  Non-striated 

muscle, 
nerves  of.  225. 
non-striated,  76. 

non-striated,  distribution  of, 76,96, 
102,  107,  112,  118,  123,  150,  151, 
193,  194,  196,  197,  202. 
of  hair-follicle,  96. 
smooth,  76.     See  Non-striated, 
striated,  78. 
voluntary,  78. 
of  oesophagus,  150. 
Myocardium,  80. 

Naboth,  ovules  of,  199. 

Nails,  98. 

Nasal  mucous  membrane,  epithelium,  55. 

Nasmyth's  membrane,  135. 

Needles,  36. 

Nerve-cells,  219. 

-cells  of  suprarenal  body,  213. 

-cells,  processes  of,  220. 

-cells  pyramidal,  238. 

-cells,  types,  220 


254 


INDEX 


Nerve-endings,  223.  [225. 

-endings    in    non-striated    muscle, 
-endings  in  striated  muscle,  225. 
-endings  in  skin,  94,  223,  224. 
-fibers,  216. 

-fibers,  axis-cylinder  of,  216. 
-fibers  in  osmic  acid,  23. 
-fibers  medullated,  216. 
-fibers  non-medullated,  217. 
Nerve,  acoustic,  216. 

connective  tissue  of,  218. 
funiculi,  217. 
olfactory,  217. 
optic,  216. 
plexuses,  225. 

practical  demonstration,  219. 
spinal,  228. 
-staining,  Cox,  34. 
-staining,  Golgi,  33. 
-staining,  nigrosin,  32. 
-staining,  Van  Gieson,  32. 
-staining,  Weigert's,  30. 
-trunks,  217. 
Nervi  nervorum,  219. 

Nervous  system,  216.  [22,  23. 

Nervous  tissues,   fixation    or    hardening, 

tissues,  development  of,  54,  223. 

tissues,    supporting    framework 

of,  222. 

Neurilemma,  217,  218. 
Neuroglia,  222. 

-cells,  223. 
Neurone,  221,  222. 
Neutrophile  granules,  31,  86. 
Newt's  tail  for  karyokinesis,  53. 
Nigrosin,  32. 

Nitrate  of  silver,  33,  61,  108.     * 
Nitric  acid,  24,  75. 
Nodes,  lymph-.     See  Lymphatic  nodes. 

of  Kanvier,  216. 

Non-medullated  nerves,  217.       ? 
Non-striated    muscle,    76.      See    Muscle, 

non-striated. 
Normal  salt  solution,  36. 
Nose,  epithelium  of,  55. 
Nuclei  of  cells,  49. 
Nucleoli  of  cells,  50. 
Nuclear  stains,  27. 

spindle,  52. 
Nucleus,  fibrils  of,  49. 

structure  of,  49. 

Objectives,  2,  4. 
Ocular.     See  Eye-piece. 
Odontoblasts,  135. 


(Esophagus,  150. 
Oil-immersion  objective,  4. 
-globules,  46. 
of  cedar  wood,  4. 
Oils,  essential,  35. 
Olfactory  nerve,  217. 
Optical  axis,  5. 
Optic  nerve,  216. 
Organisms  in  urine,  47. 
Origanum  oil,  35. 
Orth's  fluid,  22. 
Osmic  acid,  23. 

Osmico-bichromate  mixture,  23. 
Ossification,  73. 
Osteoblasts,  73. 
Osteoclasts,  73. 
Os  uteri,  198. 
Ovarial  tubes,  206. 
Ovary,  203. 

corpus  luteum  of,  203. 

germinal  epithelium,  203. 

Graafian  follicles  of,  203.          [206. 

practical  demonstrations  of,    203, 

tunica  albuginea,  203. 
Oviduct,  202. 
Ovula  Nabothi,  199. 
Ovum,  205. 

formation  of,  206. 
Oyster,  cilated  cells  from,  59. 

Pacchionian  bodies,  235. 
Pacinian  corpuscles.  223. 
Pal-Weigert  method,  30. 
Pancreas,  145. 

practical  demonstration  of,  146. 
Paper,  Japanese,  41. 
Papillas,  circumvallate,  149. 

filiform,  149. 

foliates,  149. 

fungiform,  149. 

of  skin,  93. 

of  tongue,  149. 

Papillary  eminences  of  kidney,  178. 
Paraffin,  cementing  or  soldering,  18. 

imbedding,  33,  25. 
Parenchyma  of  glands,  140. 
Parotid  gland,  143,  148.  [146. 

gland,  practical  demonstration  of, 
Patch,  Peyer's,  160. 
Pavement  epithelium,  56. 
Pelvis  of  kidney,  193. 
Penis,  212. 
Peptic  glands,  152. 
Perforating  fibers  of  Sharpey,  71. 
Pericardium,  60,  102,  107. 


INDEX 


255 


Perichondrium,  07. 
Pericementum,  137. 
Perimysium,  78. 
Perineurium,  218. 
Periosteal  bone,  74. 
Periosteum,  73. 
Peripheral  nerve-termini,  223. 
Peritoneum,  60,  107,  151. 
Perivascular  lymphatics,  107.       [107,  238. 
lymph-spaces  of    cerebrum, 
Peyer's  patches,  1GO. 
Pharynx,  149. 

mucous  membrane  of,  149. 
Pia  mater,  235. 
Picric  acid,  23,  29,  31,  32. 

alcohol,  23. 
Picro-carmine,  29. 
Pigment-cells  of  hair,  95. 
-cells  of  skin,  93. 
-cells  in  suprarenal  body,  215. 
Pineal  body,  embryonic  derivation,  54. 
Pipettes  for  haemocytometer,  86. 
Pituitary  body,  embryonic  derivation,  54. 
Plates,  blood-,  82. 

cartilage-  in  bronchi,  124. 
Pleura,  60,  107,  128. 
Plexuses,  sympathetic,  225. 

of  Auerbach,  154,  160. 
of  Meissner,  154,  160. 
Penciling  of  serous  surfaces,  108. 
Pole  of  the  cell,  52. 
Pollen,  48. 

Polynuclear    or    polymorphonuclear    leu- 
cocytes, 86. 
Portal  canal,  165. 
vein,  163. 

Posterior  commissure  of  spinal  cord,  227t 
columns,  227. 

median  fissure,  spinal  cord,  227. 
Potassium  bichromate,  22. 
Potato  starch,  48. 
Power,  magnifying,  7. 
Practical  demonstrations  of— 
blood,  82-91. 
blood-vessels,  105. 
bone,  75. 

bronchial  tube,  125. 
cartilage,  68. 
cerebellum,  240. 
cerebrum,  237. 
development  of  ovum,  206. 
elastic  tissue,  65. 
endothelium,  60. 
epithelium,  55-60. 
Fallopian  tube,  202. 


Practical  demoustrations  of — 

hair,  99. 

intestine,  160-16'J. 

karyokinensis,  53. 

kidney,  186. 

liver,  167,  170,  177. 

lung,  131. 

lymphatics  of  central  tendon 
of  diaphragm,  108. 

mesenteric  lymph-node,  113. 

mouth,  oesophagus,  pharynx, 
etc.,  150. 

muscle,  77-80. 

nerves,  219. 

ovary,  203,  206. 

pancreas,  146. 

parotid  gland,  146. 

skin,  98. 

spinal  cord,  229. 

spleen,  118. 

stomach,  155. 

submaxillary  gland,  146. 

suprarenal  body,  213. 

teeth,  137. 

testicle,  211,  212. 

thymus  body,  121. 

tongue  and  taste-buds,  150. 

ureter,  193. 

urinary  bladder,  195. 

uterus,  197. 

vagina,  197. 

white  fibrous  tissue,  63. 
Pregnancy,  uterus  in,  197. 
Preservation  of  tissues,  20. 
Prickle  cells  of  skin,  92. 
Prismatic  color  in  air-bubbles,  46. 
Prisms,  enamel,  137. 
Projection  fibers,  239. 
Prostate  gland,  212. 
Prostatic  concretions,  212. 
Protoplasm,  49. 

reticulation  of,  50.  [220 

Protoplasmic  processes  of  ganglion-cells, 
Proximal  convoluted  tubule,  181. 
Pseudopodia,  83. 
Pulmonary  alveoli,  128. 
artery,  128. 
Pulp  of  teeth,  135. 

of  spleen,  117. 
Purkinje,  cells  of,  242. 
Pus-corpuscles,  84. 
Pyloric  glands,  152. 
Pyramidal  tracts,  228. 
Pyramid  of  Ferrein,  179. 
of  Malpighi,  179. 
Pyroxylin,  26. 


256 


INDEX 


Quick  hardening  with  alcohol,  21. 

hardening  with  formaldehyde,  22. 

Racemose  glands,  143. 

Ranvier's  nodes,  216. 

Rapid  hardening  with  alcohol,  21. 

with  formaldehyde,  22. 
Rays,  medullary,  of  kidney,  179. 
Razor,  form  of,  10. 

stropping,  17. 
Receptaculum  chyli,  106. 
Red  blood-corpuscles,  81.     See  Blood. 

marrow,  73. 

Reproductive  organs,  197,  209. 
Reptiles,  blood  of,  82. 
Respiratory  organs,  123. 
Rete  Malphighii  of  skin,  92. 

mucosum  of  skin,  92. 

•testis,  210. 
Reticular  cartilage,  68. 

connective  tissue,  76,  113.  [113. 
Reticulum  of  adenoid  or  lymphoid  tissue, 
Retiform  tissue.  See  Reticular  connect- 

ive  tissue. 

Retzius,  lines  of,  137. 
Ribbon  sections.     See  Serial  sections. 
Ringing  mounts,  36,  43,  76. 
Root-sheath  of  hair,  95,  99. 
Rugae,  151.  . 

Sacs,  air-,  128. 
Safranin,  23,  31. 

Salamander  tail  for  karyokinesis,  53. 
Salivary  gland,  abdominal,  145. 
corpuscles,  47,  149. 
glands,  143,  148. 
Salt  solution,  normal,  36. 
Santorini,  cartilage  of,  123. 
Sarcolemma,  78. 
Sarcoplasm,  79. 
Schanze  microtome,  15. 
Schwann,  white  substance  of,  216. 
Sebaceous  glands,  98. 
Sebum,  98. 
Section  cutting,  10. 

free-hand,  10. 

with  microtomes,  12. 

in  series,  15. 
-lifter,  41. 
Sections,  frozen,  19. 

serial,  15,  26.  * 

to  place  on  slide,  41. 
Seminiferous  tubules,  211. 
Sensory  nerve-terminations,  223. 
Serial  sections,  15,  26. 


Serous  glands,  145,  148. 

membranes,  60,  107. 
membranes,  lymphatics  of,  108. 
Sharpening  knives,  16. 
Sharpey's  fibers,  71. 
Sheath,  dentinal,  135. 

of  Schwann,  216. 
Silk  fibers,  47. 

Silver,  mesentery  stained  with,  61. 
nitrate,  33. 

staining,  33,  61,  108,  134. 
staining  solution,  33. 
Skeletal  muscle,  78. 
Sketching  from  microscope,  9. 
Skin,  arrector  pili,  96. 

blood-vessels  of,  94. 
corium,  92. 
chamois,  43. 
eleidin  granules,  92. 
epidermis,  92. 
hair-follicles,  95. 
injected,  94. 
keratin  of,  92. 
negro,  93. 
nerves  of,  94. 
papillse  of,  93. 
pigment  of,  93. 
practical  demonstration,  98. 
sebaceous  glands,  98. 
stratum  corneum,  92. 
stratum  granulosum,  92. 
stratum  lucidum,  92. 
stratum  Malpighii,  92. 
sudoriferous  glands,  97. 
sweat-glands,  97. 
tactile  corpuscles  of,  94,  223. 
Slides,  41. 
Small  intestine,  156. 

Smooth  muscle.    See  Muscle,  non-striated. 
Sole-plate,  225. 
Solitary  glands,  160. 
Solution,  Erlicki's,  24. 

Ehrlich-Biondi-Heidenhain,  32. 
Flemming's,  23. 
Miillers,  22. 
normal  salt,  36. 
Orth's,  22. 
Stirling's,  25. 
Toison's,  87. 
Space,  subarachnoid,  235. 

subdural,  235. 

Spaces,  interglobular,  137. 

lymph-,  106. 

venous,  117. 

Special  connective  tissues,  76. 


INDEX 


257 


Specimens,  permanent,  35. 
Spermatogenic  cells,  212. 
Spermatozoa,  211. 
Sphincter  of  renal  papillae,  193. 

of  urinary  bladder,  195. 
Spider  cells,  223. 
Spinal  cord,  226. 

anterior  column,  227. 

anterior  gray  commissure,  227. 

anterior  median  fissure,  227. 

ascending  antero-lateral  tract, 

Burdach's  column,  228.    [228. 

central  canal  of,  227,  232. 

Clarke's  column,  232. 

collateral  fibers,  234. 

columns  of,  227,  228. 

commissures  of,  227,  228. 

crossed  pyramidal  tract,  228. 

descending       antero  -  lateral 
tract,  228. 

direct  cerebellar  tract,  228. 

direct  pyramidal  tract,  228. 

funiculus  cuneatus,  228. 

funiculus  gracilis,  228. 

ganglion-cells,  232. 

GolPs  column,  228. 

Gower's  column,  228. 

gray  commissures,  227. 

gray  matter,  226. 

lateral  columns,  227. 

nerve-fibers  of,  231. 

nerve-roots  of,  228. 

posterior  column,  227. 

posterior  median  fissure,  227. 

practical  demonstration,  229. 

staining  of,  30,  32,  33,  229. 

substantia     gelatinosa      Rol- 
andi,  232. 

substantia     gelatinosa     cen- 
tralis,  232. 

Turck's  column,  228. 

white  commissure,  228. 

white  matter  of,  226. 
Spiral  tubule,  181. 
Spleen,  117. 

Malpighian  bodies,  118. 
practical  demonstration,  118. 
Spongy  bone,  72. 
Spot,  germinal,  205. 
Squamous  epithelium,  55. 
Staining  agents,  27. 

aniline  dyes,  31. 
borax-carmine,  29,  39. 
carmine,  29,  39. 
Cox-Golgi,  34. 


Staining,  double,  38. 

Ehrlich-Biondi-Heidenhain,32,85 
•    eosin,  28,  38. 

fresh  tissue,  20. 

fuchsin,  31. 

general  or  ground,  27. 

gentian  violet,  31. 

Golgi,  33. 

haematoxylin,  28,  36. 

heematoxylin  and  eosin,  38. 

in  bulk,  29. 

methylene  blue,  31,  84. 

nuclear,  27. 

nigrosin,  32. 

osmic  acid  in  nerve  tissue,  23. 

Pal,  30. 

picro-carmine,  29. 

selective,  27. 

silver,  33,  61,  108,  134. 

safranin,  23,  31. 

triacid,  tricolor,  triple,  32,  85. 

Van  Gieson,  32. 

Weigert's  nerve-,  30. 
Starch,  48. 
Stirling  microtome,  12. 

dissociating  fluid,  25. 
Stomach,  151. 

practical  demonstration,  155. 

lymphatics  of,  156. 

mucous  membrane  of,  152. 

nerves  of,  154. 

peptic  glands.  153. 

pyloric  glands,  154. 
Stomata,  62,  109. 
Stratified  epithelium,  55. 
Stratum  corneum  of  skin,  92. 

granulosum,  92. 

lucidum,  92. 

Malpighii,  92. 

Striated  or  striped  muscle,  78.     See  Mus- 
cle, striated. 

cardiac  muscle,  80. 
Stripes  of  Baillarger,  237. 
Stropping  knives,  17. 
Subarachnoidal  space,  235. 
Subdural  space,  235. 
Sublingual  gland,  148. 
Sublobular  vein,  163. 
Submaxillary  glands,  144,  148. 

glands,  practical  demonstra- 
tion, 146. 

Substance,    cement-.       See    Cement-sub- 
stance. 

white,  of  Schwann,  216. 
Substances,  extraneous,  47. 


258 


INDEX 


Substantia,  gelatinosa,  232. 
Succus  entericus,  156. 
Sudoriferous  glands,  97. 
Sulphate  of  copper,  24. 
Supernumerary  spleens,  118. 
Suprarenal  body,  213. 

capsule,  213. 

Sustentacular  cells  of  testicle,  212. 
Sweat-glands,  97. 
Sympathetic  system,  217. 
System,  cerebro-spinal,  226-243. 
.     circulatory,  102. 

digestive,  135-177. 

Haversian,  71. 

lymphatic,  106. 

nervous,  216. 

respiratory,  123. 

reproductive,  197,  209. 

sympathetic  nervous,  217. 

Tactile  corpuscles,  94,  223. 
Tangential  fibers,  238. 
Taste-buds,  149. 
Teasing,  9. 
Technology,  1. 
Teeth,  135. 

cementum,  137. 
crusta  petrosa,  135. 
decalcification  of,  137. 
dentinal  fibers,  135. 
dentinal  tubules,  135. 
dentine,  135. 
enamel,  137. 

interglobular  spaces.  137. 
membrane  of  Nasmyth,  135. 
odontoblasts,  135. 
pericementum,  137. 
practical  demonstration  of,  137. 
pulp,  135. 

stripes  of  Eetzius,  137. 
Teichmann's  crystals,  90. 
Tendon,  62. 

Tesselated  epithelium,  56. 
Testicle,  209. 

coni  vasculosi,  210. 
mediastinum  of,  209. 
seminiferous  tubules  of,  210,  211. 
spermatozoa,  211. 
spenuatogenesis,  212. 
tunica  albuginea,  209. 
tunica  vaginalis,  209. 
vasa  efferentia,  210. 
Thermal  currents,  46. 
Thoracic  cavity,  60,  107,  128. 
duct,  106,  107. 


Thymus  body,  121. 
Thyme  oil,  35. 
Thoma  microtome,  14. 
Thyro-glossal  duct,  148. 
Thyroid  body,  148. 

body,  colloid  secretion  of,  148. 
Tissue,     adenoid.     See  Lymphoid  tissue. 

adipose,  65. 

areolar,  62. 

connective,  62. 

definition  of,  53. 

elastic,  63. 

embryonic,  76. 

erectile,  212. 

fat-,  65. 

fibrous,  62. 

fixation  of,  20. 

fresh,  20. 

hardening  of,  20. 

lymphoid.    See  Lymphoid  tissue. 

mucoid,  76. 

muscular,  76. 

nerve.,  216. 

white  fibrous,  62. 

yellow  elastic,  63. 
Tissues,  classification  of,  53. 

dehydration  of,  35,  38. 

embryonic  derivation  of,  54. 

varieties  of,  53. 
Toison's  fluid,  87. 
Tongue,  149. 

muscle  of,  79. 
Tonsil  of  Luschka,  149. 
Tonsils,  149. 
Tooth.     See  Teeth. 
Touch  corpuscles,  94,  223. 
Trabeculse  of  lymph-nodes,  112. 

splenic,  117. 
Trachea,  123. 

cartilages  of,  68,  123. 
Tracts  of  the  spinal  cord,  228. 
Transitional  epithelium,  55,  193,  195. 
Tricolor  or  triacid  stain  of  Ehrlich,  etc., 
True  skin,  92.  [32,  85. 

Tube,  bronchial,  123. 
Tubular  glands,  140. 
Tubule,  distal  convoluted,  182. 

Fallopian,  202. 

gastric,  152. 
Henle's  loop,  181. 

proximal  convoluted,  181 

spiral,  181. 

straight,  of  kidney,  182. 
straight,  of  testicle,  210. 
Tubules,  seminiferous,  211. 


INDEX 


259 


Tubules,  uriniferous,  180,  182. 
Tunica  albuginea,  203,  209. 
Tiirck,  column  of,  228. 
Turpentine  carbol-,  35. 
Turn-table,  36. 
Tunica  vaginalis,  209. 
vasculosa,  210. 
Typical  cell,  49. 

Unstriated  or  unstriped  muscle,  76.     See 

Muscle,  non-striated. 
Umbilical  cord,  76. 
Unipolar  nerve-cells,  220. 
Ureter,  193. 
Urethra,  196. 

glands  of,  196. 
Urinary  bladder,  194. 

organs,  178-196. 
Urine,  bacteria  in,  47. 

course  of,  in  kidney,  185. 
Uriniferous  tubules  of  kidney,  180. 
Uterus,  197. 

Vagina,  197. 
Valves  of  heart,  102. 

of  lymphatics,  107,  109. 

of  veins,  104. 
Van  Gieson's  stain,  32. 
Vasa  vasorum,  105. 
Vascular  system,  102,  106. 
Vas  deferens,  209. 
Vasa  efferentia,  210. 
Vegetable  fibers,  47. 
spores,  48. 
Veins,  104. 

hepatic,  163. 

interlobular,  163. 

intralobular,  163. 

portal,  163. 

sublobular,  163. 

valves  of,  104. 


Venae  stellataa  of  kidney,  184. 
Venous  spaces  of  spleen,  117. 
Venulte  recta  of  kidney,  184. 
Venules,  102. 
Vermiform  appendix,  ILL'. 
Vesicle,  germinal,  205. 
Vesicles,  air  ,  128. 
Villi  of  intestine,  156. 
Vital  movements,  47. 

Voluntary  muscle,  78.     See  Muscle,  stri- 
ated. 

Wall  of  cell,  49. 

Wandering  cells,  83,  104. 

Weigert-Pal  method,  30. 

Welsbach  gas-burner,  4. 

Wharton's  jelly,  76. 

Wheat  starch,  48. 

White  blood-corpuscles,  83,  104. 

commissure  of  spinal  cord,  228. 

fibrous  tissue,  62. 

matter  of  brain,  235. 

matter  of  spinal  cord,  226. 

substance  of  Schwann,  216. 
Wood  fibers,  47. 
Wool  fibers,  47. 
Wrisberg,  cartilage  of,  123. 

Xylol,  35. 

balsam,  35. 

Yeast,  48. 

Yellow  elastic  tissue,  63. 

Zinc  cement,  36. 
Zona  fasciculata,  213. 

glomerulosa,  213. 

pellucida,  205. 

reticularis,  213. 

vasculosa,  203. 


DATE   DUE  SLIP 

UNIVERSITY  OF  CALIFORNIA  MEDICAL  SCHOOL  LIBRARY 

THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


flOV  10  1930 

FEB  1      1932 

MAY 


!934 

x- ..:     .  i*39 
193^ 

MAY  i  8  1937 
DEC1 


194V 
1941 
13  194, 

GCT2V  id*} 

SEP  2  - 
5 


Aavaan  IOOHOS  IVOIQBW  VINUOJIIVO  do  AIISHBAIND 


Hal 


